CN108513403A - The control circuit and control method of power inverter - Google Patents
The control circuit and control method of power inverter Download PDFInfo
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- CN108513403A CN108513403A CN201810341641.1A CN201810341641A CN108513403A CN 108513403 A CN108513403 A CN 108513403A CN 201810341641 A CN201810341641 A CN 201810341641A CN 108513403 A CN108513403 A CN 108513403A
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/37—Converter circuits
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
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Abstract
This application discloses a kind of control circuit of power inverter and control methods.The technical solution of the embodiment of the present invention passes through when the electric current that the input voltage of power inverter and the difference of output voltage are more than the first reference voltage or flow through the second power tube is more than the first reference current, control the shutdown of the first power tube, and the driving voltage of the second power tube follows input voltage regulation, the second power tube is set to be operated in saturation state, play the role of constant-current source, to realize that the electric current for flowing through the second power tube remains steady state value.When the output of the power inverter connects LED load, by serving as constant-current source by the second power tube, it can save with the concatenated constant-current source of LED load to effectively simplify circuit design, improve system effectiveness.
Description
Technical field
The present invention relates to power electronic technique, and in particular to LED drive circuit technology, more particularly, to a kind of power
The control circuit and control method of converter.
Background technology
In flash application, LED is widely used because having many advantages, such as low-power consumption, due to stroboscopic speed is fast.By
There is high forward voltage and electric current in LED, and the equipment such as mobile phone, camera only have given cell voltage, generally use BOOST to become
Parallel operation is boosting given cell voltage to drive LED load.Also, it since LED is current drive-type device, needs
Current constant control is carried out to LED drive current.As shown in Figure 1, being a common constant current driver circuit for LED comprising one
BOOST converter and a constant-current source.The forward voltage of LED is VF, the reference voltage of error amplifier is VREF.When input electricity
Vin is pressed to be less than (VF+VREF) when, BOOST converter works to boost, at this point, switching tube Q1 and Q2 are in switch shape
State, output voltage Vout are equal to (V in stable stateF+VREF), the input voltage of constant-current source is equal to VREF.When input voltage vin is more than
(VF+VREF) when, switching tube Q1 is closed, and switching tube Q2 is fully on, and constant-current source can be carried out with the variation of input voltage vin
It adjusts, to keep LED current constant.But in this driving circuit, on the one hand, the introducing of constant-current source can increase circuit control
Complexity, area and the cost of system；On the other hand, switching tube Q2 is fully on will produce power attenuation, reduce the work of circuit
Efficiency.
Invention content
In view of this, an embodiment of the present invention provides a kind of control circuit of power inverter and control method, pass through control
It makes the second power tube in the power inverter and is operated on off state or saturation state, realize current constant control without extraly
Constant-current source is introduced, effectively to simplify circuit design, improves system effectiveness.
According to a first aspect of the embodiments of the present invention, a kind of control circuit of power inverter, the power conversion are provided
Device includes the first power tube and the second power tube, wherein
Current sampling circuit is coupled with second power tube, for sampling the electric current for flowing through second power tube, with
Obtain current sampling signal；
Driving circuit receives the input voltage of the power inverter, output voltage and the current sampling signal, works as institute
When stating the difference of input voltage and output voltage more than the first reference voltage or the current sampling signal is more than the first reference
When electric current, the driving circuit controls the first power tube shutdown, and the driving voltage for controlling second power tube follows
The input voltage regulation.
Preferably, the driving voltage for controlling second power tube follows the input voltage regulation to include：Described in control
Second power tube is operated in saturation state so that the electric current for flowing through second power tube remains steady state value.
Preferably, when the driving voltage of second power tube is less than its conduction threshold and flows through second power tube
Electric current when being less than the second reference current, the driving circuit controls the first power tube and second power tube is operated in switch
State.
Preferably, the current sampling circuit includes：
Sampling resistor is coupled with second power tube, for sampling the electric current for flowing through second power tube；
Filter circuit is connected in parallel with the sampling resistor, and the signal for obtaining the sampling resistor is filtered into directly
Signal is flowed as the current sampling signal.
Preferably, the driving circuit includes error feedback circuit, is used for the current sampling signal and reference voltage
Compare, to generate the error feedback signal.
Preferably, the driving circuit includes bypass control signal generation circuit and bypass drive voltage generating circuit；
When the current sampling signal be more than the first reference current when or the input voltage and output voltage difference
When more than the first reference voltage, the bypass control signal generation circuit generates the bypass control signal；
The bypass drive voltage generating circuit receives the bypass control signal, by by the drive of first power tube
Dynamic voltage connects reference ground to turn off first power tube and control second power tube according to the error feedback signal
Driving voltage follows the input voltage regulation.
Preferably, the driving circuit includes pwm signal generation circuit, for being generated according to the error feedback signal
Pwm signal.
Preferably, the drive voltage generating circuit includes that voltage up control signal generation circuit and boosting driving voltage generate
Circuit；
It is less than second when the driving voltage of second power tube is less than its conduction threshold and the current sampling signal
When reference current, the voltage up control signal generation circuit generates the voltage up control signal；
The boosting drive voltage generating circuit controls the first power according to the voltage up control signal and the pwm signal
Pipe and second power tube are operated on off state.
Preferably, the power inverter is BOOST topologys or FLYBACK topologys.
Preferably, second power tube is the MOSFET of two-way shutdown, by the substrate for selecting second power tube
So that the body diode reverse of second power tube blocks, saturation state is operated in control second power tube.
Preferably, the average current for flowing through second power tube is equal to the output current of the power inverter and is averaged
Value.
Preferably, first reference voltage is arranged according to the conducting resistance of second power tube.
According to a second aspect of the embodiments of the present invention, a kind of control method for power inverter, the power are provided
Converter includes the first power tube and the second power tube, wherein
Sampling flows through the electric current of second power tube, to obtain current sampling signal；
Receive the input voltage of the power inverter, output voltage and the current sampling signal；
It is when the difference of the input voltage of the power inverter and output voltage is more than the first reference voltage or described
When current sampling signal is more than the first reference current, the first power tube shutdown is controlled, and control second power tube
Driving voltage follows the input voltage regulation.
Preferably, the driving voltage for controlling second power tube follows the input voltage regulation to include：Described in control
Second power tube is operated in saturation state so that the electric current for flowing through second power tube remains steady state value.
Preferably, when the driving voltage of second power tube is less than its conduction threshold and flows through second power tube
Electric current when being less than the second reference current, control first power tube and second power tube and be operated on off state.
The technical solution of the embodiment of the present invention in the input voltage of power inverter and the difference of output voltage by being more than
When first reference voltage or the electric current for flowing through the second power tube are more than the first reference current, control the first power tube shutdown, and
The driving voltage of second power tube follows input voltage regulation, so that the second power tube is operated in saturation state, plays constant-current source
Effect, to realize that the electric current for flowing through the second power tube remains steady state value.When the output of the power inverter connects LED load
When, by serving as constant-current source by the second power tube, can save with the concatenated constant-current source of LED load to effectively simplify circuit
Design, improves system effectiveness.
Description of the drawings
By referring to the drawings to the description of the embodiment of the present invention, the above and other purposes of the present invention, feature and
Advantage will be apparent from, in the accompanying drawings：
Fig. 1 is common constant current driver circuit for LED；
Fig. 2 is the circuit diagram of the power inverter with control circuit of the embodiment of the present invention；
Fig. 3 a and Fig. 3 b are the circuit diagrams of the current sampling circuit of the embodiment of the present invention；
Fig. 4 is the circuit diagram of the power inverter comprising feedback circuit concrete structure of the embodiment of the present invention；
Fig. 5 is the circuit diagram of the mode switching circuit of the embodiment of the present invention；
Fig. 6 is the circuit diagram of the drive voltage generating circuit of the embodiment of the present invention；
Fig. 7 is the working waveform figure of the power inverter of the embodiment of the present invention；
Fig. 8 is the control method flow chart of the power inverter of the embodiment of the present invention.
Specific implementation mode
Below based on embodiment, present invention is described, but the present invention is not restricted to these embodiments.Under
Text to the present invention datail description in, it is detailed to describe some specific detail sections.Do not have for a person skilled in the art
The description of these detail sections can also understand the present invention completely.In order to avoid obscuring the essence of the present invention, well known method, mistake
There is no narrations in detail for journey, flow, element and circuit.
In addition, it should be understood by one skilled in the art that provided herein attached drawing be provided to explanation purpose, and
What attached drawing was not necessarily drawn to scale.
It will also be appreciated that in the following description, " circuit " refer to passed through by least one element or sub-circuit it is electrical
The galvanic circle that connection or electromagnetism connect and compose.It " is connected when claiming element or another element of circuit " being connected to " or element/circuit
" between two nodes when, it can be directly coupled or connected another element or may exist intermediary element, element it
Between connection can be physically, in logic or its combination.On the contrary, when claiming element " being directly coupled to " or " directly connecting
Be connected to " another element when, it is meant that the two be not present intermediary element.
Unless the context clearly requires otherwise, "include", "comprise" otherwise throughout the specification and claims etc. are similar
Word should be construed as the meaning for including rather than exclusive or exhaustive meaning；That is, being containing for " including but not limited to "
Justice.
In the description of the present invention, it is to be understood that, term " first ", " second " etc. are used for description purposes only, without
It can be interpreted as indicating or implying relative importance.In addition, in the description of the present invention, unless otherwise indicated, the meaning of " multiple "
It is two or more.
Fig. 2 is the circuit diagram of the control circuit of the power inverter of the embodiment of the present invention.As shown in Fig. 2, the present embodiment
Power inverter 2 includes power stage circuit, and the power stage circuit is BOOST topologys, specifically includes inductance Lf, first end with
The input terminal of the power inverter connects；First power tube Q1, the first power end are connect with the second end of the inductance Lf,
Second power end is connect with the reference ground of the power inverter 2；Second power tube Q2, the first power end and the inductance Lf
Second end connection, the second power end connect with the output end of the power inverter 2.The control circuit includes current sample
Circuit 20 and driving circuit 21.Wherein, the current sampling circuit 20 is coupled with the second power tube Q2, is used for sample streams
Electric current through the second power tube Q2, to obtain current sampling signal (by the first sampled signal Vi+ and the second sampled signal
The difference of Vi- characterizes)；The driving circuit 21, receives the input voltage vin of the power inverter 2, output voltage Vout,
The threshold voltage Vgth and the current sampling signal of the second power tube Q2, when the input voltage vin and output voltage
When the difference of Vout is more than the first reference voltage or when the current sampling signal is more than the first reference current, the driving electricity
Road 21 controls the first power tube Q1 shutdowns, and the driving voltage VQ2 for controlling the second power tube Q2 follows the input
Voltage Vin is adjusted.
Specifically, the driving circuit 21 includes error feedback circuit 211, pwm signal generation circuit 222, pattern switching
Circuit 223 and drive voltage generating circuit 224.The error feedback circuit 211 receives the current sampling signal and (is adopted by first
The difference of sample signal Vi+ and the second sampled signal Vi- characterize), by comparing the current sampling signal and first reference
Electric current, with output error signal Vc.The pwm signal generation circuit receives the error signal Vc, and generates pwm signal.Institute
State the input voltage vin that mode switching circuit 223 receives the power inverter 2, output voltage Vout and the current sample
Signal, when the input voltage vin and the difference of output voltage Vout are more than the first reference voltage or the current sample
When signal is more than the first reference current, the mode switching circuit 223 exports bypass control signal Bypass.The driving voltage
Generation circuit 224 receives the bypass control signal Bypass, and generates the first driving voltage VQ1 accordingly and control first work(
The driving voltage that rate pipe Q1 shutdowns and the second driving voltage VQ2 control the second power tube Q2 follows the input voltage vin
It adjusts.
Wherein, the pwm signal generation circuit can be by by the error signal and sawtooth signal or triangular signal
Compare to generate, or is realized using other common technical solutions.
In addition, the mode switching circuit 223 can also receive the driving voltage VQ2 of the second power tube Q2, work as institute
Driving voltage VQ2 is stated less than its conduction threshold Vgth and flows through the electric current of the second power tube Q2 less than the second reference current
When, the mode switching circuit 223 exports voltage up control signal Boost.At this point, described in the drive voltage generating circuit reception
Voltage up control signal Boost and the pwm signal, and the first driving voltage VQ1 and the second driving voltage VQ2 controls are generated accordingly
The first power tube Q1 and the second power tube Q2 are operated on off state.
In the present embodiment, when the second driving voltage VQ2 for controlling the second power tube Q2 follows the input
When voltage Vin is adjusted, the second power tube Q2 is operated in saturation state, can play the role of constant-current source.Preferably as one
Scheme, the MOSFET of two-way shutdown can be selected as second power tube, pass through the second driving voltage VQ2 selections
The substrate of the second power tube Q2 makes the body diode reverse of the second power tube Q2 block, to control second work(
Rate pipe Q2 is operated in saturation state.
In the present embodiment, when the output of the power inverter terminates LED load, compared to technology shown in FIG. 1
Scheme, above-mentioned control circuit can in the case of no constant-current source, by making second power tube be operated in saturation state,
Play the role of constant-current source, and the output current of the power inverter is made to keep constant.
In another embodiment, the power stage circuit of the power inverter can be FLYBACK topologys.Certainly, exist
When the average current that satisfaction flows through second power tube is equal to the output current of the power inverter, the power stage circuit
May be used it is other meet the topological structure of the condition, and be not limited to enumerated BOOST topologys or FLYBACK topological structures.
Fig. 3 a and Fig. 3 b are the circuit diagrams of the current sampling circuit of the embodiment of the present invention.
Wherein, Fig. 3 a are resistance sampling method, and current sampling circuit includes sampling resistor Rs and filter circuit, the sampling electricity
Resistance Rs is connected between the second power end and the output end of the power inverter of the second power tube Q2, the filtered electrical
Road is connected in parallel on the both ends of the sampling resistor Rs.In the present embodiment, the filter circuit is RC filter circuits, and being used for will be described
The signal that sampling resistor Rs is sampled is filtered into direct current signal.Specifically, the RC filter circuits include filter resistance R1 and
Filter capacitor C1, one end of the filter resistance R1 are connect with one end of the sampling resistor Rs, the other end and the filtered electrical
Hold one end connection of C1, the other end of the filter capacitor C1 is connect with the other end of the sampling resistor Rs.The filtered electrical
Hold output end of the both ends of C1 as the current sampling circuit, exports the first sampled signal Vi+ and the second sampled signal respectively
Vi-, when stable state, the difference of the first sampled signal Vi+ and the second sampled signal Vi- characterize the current sampling signal, i.e.,
Flow through the current average of second power tube.Certainly, skilled person will appreciate that, the filter circuit can be used other
Technical solution is realized, and is not limited to Fig. 3 a illustrated embodiments.
Fig. 3 b are mirror image sampling method, and the current sampling circuit includes third power tube Q3, the 4th power tube Q4, and error is put
Big device EA, sampling resistor Rs and filter circuit.Wherein, the third power tube Q3 and the second power tube Q2 constitutes mirror image knot
Structure, that is, the control terminal of the third power tube Q3 is connected with the control terminal of the second power tube Q2, the third power tube Q3
The first power end be connected with the first power end of the second power tube Q2, the second power end Q3 of the third power tube with
The first power end of the 4th power tube Q4 is connected；Two input terminals of the error amplifier EA are respectively connected to described
The second power end of two power tube Q2 and the third power tube Q3, output end are connected to the control of the 4th power tube Q4
End；The sampling resistor Rs is connected between the second power end and reference ground of the 4th power tube Q4；The filter circuit
The both ends of the sampling resistor are connected in parallel on, concrete structure is identical as the filter circuit in Fig. 3 a, and details are not described herein.Compared to
Resistance sampling method shown in Fig. 3 a, the loss of mirror image sampling method are smaller.
Fig. 4 is the circuit diagram of the power inverter comprising feedback circuit concrete structure of the embodiment of the present invention.Wherein, it feeds back
Circuit 211 includes the first error amplifier A1 and reference voltage Vref.The anode of the reference voltage Vref receives described first
Sampled signal Vi+, cathode connect the first input end (for example, inverting input) of the first error amplifier A1；Described
The second input terminal (for example, in-phase input end) of one error amplifier A1 receives the second sampled signal Vi-, output end output
Error feedback signal Vc.
Fig. 5 is the circuit diagram of the mode switching circuit of the embodiment of the present invention.As shown in figure 5, the mode switching circuit 223
Including bypass control signal generation circuit 501 and voltage up control signal generation circuit 502.
Wherein, bypass control signal generation circuit 501 includes the second comparator A2, third comparator A3 and/or door.It is described
The first input end (for example, in-phase input end) of second comparator A2 receives the first sampled signal Vi+ and first with reference to electricity
The difference of Vi_ref1 is flowed, the second input terminal (for example, inverting input) receives the second sampled signal Vi-, when described first
The difference of sampled signal Vi+ and the second sampled signal Vi- (adopt by the electric current for the electric current that i.e. characterization flows through second power tube
Sample signal) when being more than the first reference current Vi_ref1, the output signal of the second comparator A2 is that high level is effective.
The first input end (for example, in-phase input end) of the third comparator A3 receives the input voltage vin with first with reference to electricity
The difference of Vv_ref1, the second input terminal (for example, inverting input) is pressed to receive the output voltage Vout, when input electricity
When pressure and the difference of the output voltage are more than the first reference voltage Vv_ref1, the output letter of the third comparator A3
Number for high level it is effective.The output signal of the second comparator A2 and the output signal of the third comparator A3 are input to
Described or door, when any of two output signals are that high level is effective, described or door exports bypass control signal.Also
It is to say, when the current sampling signal (is characterized) by the difference of the first sampled signal Vi+ and the second sampled signal Vi-
When more than the first reference current Vi_ref1 or the input voltage vin and the difference of output voltage Vout are more than the first reference
When voltage Vv_ref1, the bypass control signal generation circuit 501 generates the bypass control signal Bypass.
The voltage up control signal generation circuit 502 include the 4th comparator A4, the 5th comparator A5 and with door.Described
The first input end (for example, in-phase input end) of four comparator A4 receives the second sampled signal Vi-, the second input terminal (example
Such as, inverting input) receive the first sampled signal Vi+ and the second reference current Vi_ref2 difference, when it is described first sampling believe
(i.e. characterization flows through the current sample of the electric current of second power tube and believes the difference of number Vi+ and the second sampled signal Vi-
Number) when being less than the second reference current Vi_ref2, the output signal of the 4th comparator A4 is that high level is effective.It is described
The first input end (for example, in-phase input end) of 5th comparator A5 receives the threshold voltage Vgth of the second power tube Q2,
Second input terminal (for example, inverting input) receives the driving voltage VQ2 of the second power tube Q2, when the driving voltage
When VQ2 is less than the threshold voltage Vgth, the output signal of the 5th comparator is that high level is effective.4th comparator
Output signal and the output signal of the 5th comparator be input to described and door, when in two output signals being height
It is described to export voltage up control signal Boost with door when level is effective.That is, when the driving electricity of the second power tube Q2
When pressing VQ2 to be less than its conduction threshold Vgth and the current sampling signal to be less than the second reference current Vi_ref2, the boosting
It controls signal generating circuit 502 and exports voltage up control signal Boost.
In the present embodiment, the first reference voltage Vv_ref1 is arranged according to the conducting resistance of second power tube,
For example, can be 270mV.The reference voltage Vref is more than the second reference current Vi_ref2 but less than first with reference to electricity
Flow Vi_ref1.
Fig. 6 is the circuit diagram of the drive voltage generating circuit of the embodiment of the present invention.As shown in fig. 6, the driving voltage production
Raw circuit 224 includes bypass drive voltage generating circuit 601 and boosting drive voltage generating circuit 602.
Wherein, the bypass drive voltage generating circuit 601 includes the first buffer B1 and the second buffer B2, and described the
The input of one buffer B1 terminates reference ground, enables termination bypass control signal Bypass, and output end generates described for controlling
The first driving voltage VQ1 of first power tube Q1 controls the first power tube Q1 shutdowns；The input of the second buffer B2
The error signal Vc is terminated, the termination bypass control signal Bypass is enabled, output end is generated for controlling described second
The second driving voltage VQ2 of power tube Q2, the driving voltage for controlling the second power tube Q2 follow the input voltage vin tune
Section.That is, the bypass drive voltage generating circuit by the driving voltage VQ1 of the first power tube Q1 by connecing reference ground to close
Break the first power tube Q1 and according to the error feedback signal Vc control the driving voltage VQ2 of the second power tube Q2 with
It is adjusted with the input voltage vin.
The boosting drive voltage generating circuit 602 includes dead time generation circuit, and third buffer B3 and the 4th is slow
Rush device B4.The input terminal of the dead time generation circuit receives the pwm signal, and output end connects the third buffer respectively
The input terminal of B3 and the 4th buffer B4, the production for making the first driving voltage Q1 and the second driving voltage Q2
It is raw that there is certain time interval；The Enable Pin of the third buffer B3 receives the voltage up control signal Boost, output end
Generate the first driving voltage VQ1 for controlling the first power tube Q1；Described in the enabled termination of the 4th buffer B2
Voltage up control signal Boost, output end generate the second driving voltage VQ2 for controlling the second power tube Q2.That is, described
The drive voltage generating circuit 602 that boosts controls the first power tube Q1 according to the voltage up control signal Boost and the pwm signal
It is operated on off state with the second power tube Q2
Fig. 7 is the working waveform figure of the power inverter of the embodiment of the present invention.
During t0~t1:Power inverter is in stable state, and operating mode is boosting (Boost) pattern；
During t1~t2:Input voltage vin slowly rises, and control circuit makes output voltage Vout by adjusting duty ratio
It keeps stablizing with the electric current IQ2 for flowing through the second power tube Q2.When duty ratio, which reaches minimum, to be adjusted still further below, output
Voltage Vout and electric current IQ2 can rise with input voltage vin.(the example when electric current IQ2 rises to the first reference current Iref1
Such as, the t2 moment in Fig. 7) or the difference of input voltage vin and output voltage Vout when being more than the first reference voltage, the control
The operating mode of power inverter described in circuit control is switched to bypass (Bypass) pattern；
During t2~t3:The power inverter is operated in bypass (Bypass) pattern, and the control circuit controls institute
It states the first power tube Q1 to close, and adjusts the driving voltage of the second power tube Q2 according to the input voltage vin, by making
Second power tube Q2 is operated in saturation state, is equivalent to a constant-current source, and the electric current IQ2 is made to stablize in setting value.
During t3~t4:Input voltage vin is constant, and the power inverter is maintained at bypass (Bypass) pattern and goes forward side by side
Enter new stable state.
During t4~t5:Input voltage vin is gradually reduced, and the power inverter continues to be operated in bypass
(Bypass) pattern, the control circuit control the first power tube Q1 and close, and adjust institute according to the input voltage vin
The driving voltage for stating the second power tube Q2 makes the electric current IQ2 continue to stablize in setting value；
During t5-t6：The driving voltage VQ2 of the second power tube Q2 is less than its conduction threshold Vgth, flows through described
The electric current IQ2 of second power tube Q2 follows the input voltage vin to decline until dropping to the second reference current Iref2, the work(
The operating mode of rate converter is switched to boosting (Boost) pattern.
During t6~t7:The input voltage vin continues to decline, and the driving voltage VQ2 of the second power tube Q2 is small
In its conduction threshold Vgth and flow through the second power tube Q2 electric current IQ2 be less than the second reference current Iref, the work(
Rate converter is operated in boosting (Boost) pattern, by adjusting duty ratio, electric current IQ2 is made to stablize in setting value；
During t7~t8:Input voltage vin is constant, and the power inverter is maintained at boosting (Boost) pattern and goes forward side by side
Enter new stable state.
Fig. 8 is the control method flow chart of the power inverter of the embodiment of the present invention.The control method includes：
Step S80：Sampling flows through the electric current of second power tube, to obtain current sampling signal；
Step S81：Receive the input voltage of the power inverter, output voltage and the current sampling signal；
Step S82：When the difference of the input voltage of the power inverter and output voltage is more than the first reference voltage
Or the current sampling signal controls first power tube shutdown, and control described second when being more than the first reference current
The driving voltage of power tube follows the input voltage regulation.
Wherein, in step S82, the driving voltage for controlling second power tube follows the input voltage regulation packet
It includes：It controls second power tube and is operated in saturation state so that the electric current for flowing through second power tube remains steady state value.
In addition, the control method can also include step S83：When the driving voltage of second power tube is connected less than it
Threshold value and when the electric current for flowing through second power tube is less than the second reference current controls first power tube and described the
Two power tubes are operated on off state.
The technical solution of the embodiment of the present invention in the input voltage of power inverter and the difference of output voltage by being more than
When first reference voltage or the electric current for flowing through the second power tube are more than the first reference current, control the first power tube shutdown, and
The driving voltage of second power tube follows input voltage regulation, so that the second power tube is operated in saturation state, plays constant-current source
Effect, to realize that the electric current for flowing through the second power tube remains steady state value.When the output of the power inverter connects LED load
When, by serving as constant-current source by the second power tube, can save with the concatenated constant-current source of LED load to effectively simplify circuit
Design, improves system effectiveness.
The foregoing is merely the preferred embodiment of the present invention, are not intended to restrict the invention, for those skilled in the art
For, the present invention can have various modifications and changes.It is all within spirit and principles of the present invention made by any modification, equivalent
Replace, improve etc., it should all be included in the protection scope of the present invention.
Claims (15)
1. a kind of control circuit of power inverter, the power inverter includes the first power tube and the second power tube, spy
Sign is,
Current sampling circuit is coupled with second power tube, for sampling the electric current for flowing through second power tube, to obtain
Current sampling signal；
Driving circuit receives the input voltage of the power inverter, output voltage and the current sampling signal, when described defeated
When entering the difference of voltage and output voltage more than the first reference voltage or the current sampling signal is more than the first reference current
When, the driving circuit controls the first power tube shutdown, and the driving voltage for controlling second power tube follow it is described
Input voltage regulation.
2. control circuit according to claim 1, which is characterized in that the driving voltage of control second power tube follows
The input voltage regulation includes：It controls second power tube and is operated in saturation state so that flow through second power tube
Electric current remain steady state value.
3. control circuit according to claim 1, which is characterized in that when the driving voltage of second power tube is less than it
Conduction threshold and when the electric current for flowing through second power tube is less than the second reference current, the driving circuit controls the first work(
Rate pipe and second power tube are operated on off state.
4. control circuit according to claim 1, which is characterized in that the current sampling circuit includes：
Sampling resistor is coupled with second power tube, for sampling the electric current for flowing through second power tube；
Filter circuit is connected in parallel with the sampling resistor, and the signal for obtaining the sampling resistor is filtered into direct current letter
Number conduct current sampling signal.
5. control circuit according to claim 1, which is characterized in that the driving circuit includes error feedback circuit, is used
In by the current sampling signal compared with reference voltage, to generate the error feedback signal.
6. control circuit according to claim 6, which is characterized in that the driving circuit includes that bypass control signal generates
Circuit and bypass drive voltage generating circuit；
When the current sampling signal is more than the first reference current or the difference of the input voltage and output voltage is more than
When the first reference voltage, the bypass control signal generation circuit generates the bypass control signal；
The bypass drive voltage generating circuit receives the bypass control signal, by the way that the driving of first power tube is electric
Reference ground is crimped to turn off first power tube and control the driving of second power tube according to the error feedback signal
Input voltage regulation described in voltage follow.
7. power inverter according to claim 5, which is characterized in that the driving circuit includes that pwm signal generates electricity
Road, for generating pwm signal according to the error feedback signal.
8. power inverter according to claim 7, which is characterized in that the drive voltage generating circuit includes that boosting is controlled
Signal generating circuit processed and boosting drive voltage generating circuit；
It is less than the second reference when the driving voltage of second power tube is less than its conduction threshold and the current sampling signal
When electric current, the voltage up control signal generation circuit generates the voltage up control signal；
The boosting drive voltage generating circuit according to the voltage up control signal and the pwm signal control the first power tube and
Second power tube is operated on off state.
9. control circuit according to claim 1, which is characterized in that the power inverter be BOOST topology or
FLYBACK topologys.
10. control circuit according to claim 1, which is characterized in that second power tube is two-way shutdown
MOSFET, by selecting the substrate of second power tube that the body diode reverse of second power tube is made to block, with control
It makes second power tube and is operated in saturation state.
11. control circuit according to claim 1, which is characterized in that flow through the average current etc. of second power tube
In the output current of the power inverter.
12. control circuit according to claim 1, which is characterized in that first reference voltage is according to second work(
The conducting resistance of rate pipe is arranged.
13. a kind of control method for power inverter, the power inverter includes the first power tube and the second power tube,
It is characterized in that,
Sampling flows through the electric current of second power tube, to obtain current sampling signal；
Receive the input voltage of the power inverter, output voltage and the current sampling signal；
When the difference of the input voltage of the power inverter and output voltage be more than the first reference voltage when or the electric current
When sampled signal is more than the first reference current, the first power tube shutdown is controlled, and control the driving of second power tube
Input voltage regulation described in voltage follow.
14. control method according to claim 13, which is characterized in that the driving voltage of control second power tube with
Include with the input voltage regulation：It controls second power tube and is operated in saturation state so that flow through second power
The electric current of pipe remains steady state value.
15. control method according to claim 13, which is characterized in that when the driving voltage of second power tube is less than
Its conduction threshold and when the electric current for flowing through second power tube is less than the second reference current, control first power tube and
Second power tube is operated on off state.
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| CN201810341641.1A CN108513403B (en) | 2018-04-17 | 2018-04-17 | Control circuit and control method of power converter |
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| CN114096040A (en) * | 2021-11-17 | 2022-02-25 | 启攀微电子（上海）有限公司 | Double-circuit independent control flash lamp drive structure |
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