Summary of the invention
The object of this invention is to provide a kind of Switching Power Supply by regulating the turn ratio to realize ultra-wide input voltage range, utilize the method for the electronic switch control transformer turn ratio, the input voltage threshold value of turn ratio saltus step is controlled by arranging transformer, and the turn ratio of secondary tandem winding, reduce the adjustable range of the pulse duty factor of PWM controller, make feedback loop control more stable, when the components and parts that circuit increases are less, Switching Power Supply is worked in ultra-wide input voltage range.
For achieving the above object, the technical solution used in the present invention is:
A kind of Switching Power Supply by regulating the turn ratio to realize ultra-wide input voltage range, it comprises the filter circuit being connected to power supply input, input voltage monitoring and optoelectronic switch control circuit, the output of filter circuit is connected with the primary side winding of transformer, the output of filter circuit is connected with pwm control circuit by mu balanced circuit, pwm control circuit is connected with feedback control loop, feedback control loop is connected to the output of Switching Power Supply, described input voltage monitoring and optoelectronic switch control circuit comprise photoelectrical coupler, the primary side winding of described transformer is connected with the drain electrode of the first switching tube, the grid of described first switching tube is connected with described pwm control circuit by switch tube driving circuit, the source electrode of described first switching tube is connected with described pwm control circuit by current sampling circuit, the source electrode of described first switching tube is connected with one end of the 4th resistor, the other end ground connection of described 4th resistor, the primary side of described transformer is by second winding of connecting successively, the tertiary winding, 4th winding composition, described second winding is connected with the output of Switching Power Supply by current rectifying and wave filtering circuit, one end of the described tertiary winding is connected with described current rectifying and wave filtering circuit, the other end is connected with turn ratio control circuit, described 4th winding is connected with described photoelectrical coupler by turn ratio control circuit, described input voltage monitoring and optoelectronic switch control circuit detect in real time to input voltage, input voltage and reference voltage are compared, and then control the switch of described photoelectrical coupler, make the second winding of described transformer secondary, the tertiary winding, 4th winding forms different loops from described turn ratio control circuit, by arranging the input voltage threshold value controlling turn ratio saltus step, change the turn ratio of described transformer secondary series connection winding, make the adjustable range of the pulse duty factor of described pwm control circuit in the reasonable scope, avoid Switching Power Supply and occur self-oscillation, make the control of feedback control loop more stable.
As a further improvement on the present invention, described filter circuit is made up of the first electric capacity, the second electric capacity, the first inductor, one termination power supply positive input terminal of described first capacitor, another termination power supply negative input end, one termination power supply positive input terminal of described first inductor, No. 1 termination of the IN end of the one end of the second capacitor described in another termination, integrated regulator and the primary side winding of the first transformer, another termination power supply ground terminal of described second capacitor.Described filter circuit is bilateral network, has both prevented the AC influence composition inputted on electric wire from entering Switching Power Supply, suppresses high-frequency noise to produce harmful effect to Switching Power Supply; Prevent again the electromagnetic interference in Switching Power Supply from passing on electrical network by power line, electrical network is polluted.
Further improve as of the present invention, described pwm control circuit is made up of PWM control integration circuit, described mu balanced circuit is made up of integrated regulator, the GND termination power supply ground terminal of described integrated regulator, the VCC end of PWM control integration circuit described in OUT termination and 8 pin of voltage compare integrated circuit; One end of OUT termination first resistor of described PWM control integration circuit, one end of CS sampling termination the 3rd resistor and the 3rd capacitor, GND termination power supply ground terminal, one end of described first resistor is connected with one end of the second resistor, the other end of described second resistor is connected with the other end of described 3rd resistor, the source electrode of described first switching tube, another termination power supply ground terminal of described 3rd capacitor; The course of work of described pwm control circuit is: the output voltage signal monitored is sent into described PWM control integration circuit by described feedback control loop, PWM control integration circuit is to the real time signal processing collected, the driving pulse dutycycle of adjustment PWM pulse width modulator, thus reaching regulated output voltage object, described integrated regulator is the operating voltage for described PWM control integration circuit with stable.
Further improve as of the present invention, described input voltage monitoring and optoelectronic switch control circuit are made up of described voltage compare integrated circuit, photoelectrical coupler, the 7th resistor, the 8th resistor, the 9th resistor, the tenth resistor, the 7th capacitor, the 5th diode, described photoelectrical coupler inside comprises a light emitting diode and a phototriode, one termination power supply positive input terminal of described 7th resistor, one end of the 8th resistor described in another termination and 3 pin of described voltage compare integrated circuit; Another termination power supply ground terminal of described 8th resistor; 2 pin of described voltage compare integrated circuit connect reference voltage, and 4 pin connect power supply ground terminal, and 8 pin connect the OUT end of described integrated regulator and one end of described 7th capacitor, and 1 pin connects the anode of described 5th diode; Another termination of described 7th capacitor connects power supply ground terminal; The negative electrode of described 5th diode connects one end of described 9th resistor; One end of tenth resistor and 1 pin of described photoelectrical coupler described in another termination of described 9th resistor; 2 pin of described photoelectrical coupler connect the other end and the power supply ground terminal of described tenth resistor.The course of work of the monitoring of described input voltage and optoelectronic switch control circuit for: first at the input in the same way of described voltage compare integrated circuit by detecting in real time institute's input voltage, the voltage produced through described 7th resistor sends into the described voltage compare integrated circuit be made up of operational amplifier, and compare with the reference voltage being added in backward end, export from 1 pin of described voltage compare integrated circuit the switch that low and high level controls described photoelectrical coupler; When input voltage is higher, the forward end voltage of described voltage compare integrated circuit is higher than backward end reference voltage, described voltage compare integrated circuit exports high level, makes the LEDs ON of described photoelectrical coupler inside, simultaneously the triode ON of described photoelectrical coupler inside; When input voltage is lower, the forward end voltage of described voltage compare integrated circuit is lower than backward end reference voltage, described voltage compare integrated circuit exports low level, make the light emitting diode not conducting of described photoelectrical coupler inside, simultaneously the triode also not conducting of described photoelectrical coupler inside.
Further improve as of the present invention, described turn ratio control circuit, current rectifying and wave filtering circuit constitute described transformer secondary control circuit, described current rectifying and wave filtering circuit is made up of the first diode, the 4th capacitor, the 5th capacitor, the second inductor, described turn ratio control circuit is by second switch pipe, first Zener diode, second diode, 3rd diode, 4th diode, 5th resistor, 6th resistor, 6th capacitor composition, No. 3 terminations of the second winding of described transformer connect Switching Power Supply negative output terminal and described 4th capacitor, one end of 5th capacitor, No. 4 terminations of described second winding connect the anode of described first diode and No. 5 terminations of the described tertiary winding, and the negative electrode of described first diode connects one end of described second inductor simultaneously, the other end of the 4th capacitor, the negative electrode of the 4th diode, 3 pin of described photoelectrical coupler, the anode of the first Zener diode, one end of 6th resistor and the 6th capacitor, the other end of the 5th capacitor described in another termination of described second inductor and Switching Power Supply positive output end, the source electrode of described second switch pipe connects the anode of the 4th diode, and drain electrode connects the negative electrode of the second diode, and grid connects the 6th resistor, the other end of the 6th capacitor, the negative electrode of the first voltage-stabiliser tube, 4 pin of described photoelectrical coupler and one end of the 5th resistor, the negative electrode of another termination the 3rd diode of the 5th resistor, the anode of the 3rd diode connects No. 8 terminations of the 4th winding, No. 7 terminations of described 4th winding connect the anode of the second diode and No. 6 terminations of the described tertiary winding, its course of work is: when input voltage is higher, described voltage compare integrated circuit exports high level, the light emitting diode of described photoelectrical coupler inside, the equal conducting of triode, Voltage Establishment is not had between the grid of described second switch pipe and source electrode, described second switch pipe cannot conducting, in the loop that the tertiary winding of described transformer is formed, no current flows through, the loop works that electric current is consisted of the second winding of described transformer, the first diode, the second inductor and load, when input voltage is lower, described voltage compare integrated circuit exports low level, the light emitting diode of described photoelectrical coupler inside, triode all not conductings, the 4th winding just by described transformer between the grid of described second switch pipe and source electrode, described current rectifying and wave filtering circuit, described mu balanced circuit sets up suitable voltage, the conducting of described second switch pipe, now by the second winding of described transformer, the tertiary winding, second diode, the voltage of the 4th diode circuit is higher than the second winding by described transformer, the voltage of the first diode circuit, described first diode is in reverse blocking state in whole loop, electric current is only by the second winding of described transformer, the tertiary winding, second diode, 4th diode, the loop works that described second inductor and load are formed.
Operation principle of the present invention is:
First input voltage is detected in real time in the present invention, voltage after the 7th resistor divider sends into the forward end of described voltage compare integrated circuit, and compare with the reference voltage being added in described voltage compare integrated circuit backward end, export from 1 pin of described voltage compare integrated circuit the switch that low and high level controls described photoelectrical coupler.
When input voltage is higher, the forward end voltage of described voltage compare integrated circuit is higher than backward end voltage, voltage compare integrated circuit exports high level, make the LEDs ON of described photoelectrical coupler inside, the phototriode also conducting thereupon of described photoelectrical coupler inside simultaneously, make there is no Voltage Establishment between the grid of second switch pipe and source electrode, the not conducting of described second switch pipe, in the loop at the tertiary winding place of described transformer secondary, no current flows through, then electric current is by described transformer second winding, first diode, the loop works that second inductor and load are formed.
When input voltage is lower, the forward end voltage of described voltage compare integrated circuit is lower than backward end voltage, described voltage compare integrated circuit exports low level, the then light emitting diode not conducting of described photoelectrical coupler inside, the phototriode also not conducting of described photoelectrical coupler inside, the grid of second switch pipe just sets up voltage difference by the 4th winding of described transformer and corresponding current rectifying and wave filtering circuit between source electrode, the conducting of second switch pipe, now by transformer second winding, the tertiary winding, second diode, the voltage in the loop of the 4th diode composition is higher than passing through described transformer second winding, the voltage of the first diode circuit, then the first diode D1 is in reverse blocking state in the loop, electric current is only by the second winding of described transformer, the tertiary winding, second diode, 4th diode, the loop works that second inductor and load are formed.
Actual described pwm control circuit is exactly the feedback signal sent here by real time feed-back loop, inner by comparing with benchmark, and the dutycycle that control PWM exports pulse realizes the stable of output voltage.Illustrate, assuming that circuit topological structure is single-ended flyback, power supply is input as 8 multiplication of voltage voltage Vin=9V ~ 72V; Output voltage Vo=15V, then inverse-excitation type circuit maximum duty cycle is designed to Dmax=42%.
(1) when usual without second switch management and control transformer turns ratio:
According to formula:
The calculating transformer turn ratio:
Again with the dutycycle of circuit under fixing transformer turns ratio calculating maximum input voltage:
Dmax≈8.3%
In this case, pulse duty factor changes between 8.3% ~ 42%.
(2) when using second switch management and control transformer turns ratio:
Assuming that the input voltage threshold value of setting turn ratio saltus step is 36V; Turn ratio N2:N3=1:1; Recalculate:
As Vin=9V ~ 36V, because secondary-side voltage is boosted jointly by described transformer second winding, the tertiary winding, therefore:
The calculating transformer turn ratio:
Again with the dutycycle of circuit under fixing transformer turns ratio calculating 36V input voltage:
Dmax≈15.3%
When input voltage is greater than 36V, when Vin=36V ~ 72V changes, because the transformer secondary tertiary winding is closed by second switch pipe, voltage is only by the boosting of transformer N2 winding, and so now the turn ratio of transformer is:
Again with the dutycycle of circuit under fixing transformer turns ratio calculating 72V input voltage:
Dmax≈15.3%
Can be learnt by above-mentioned calculating, in whole input voltage range (Vin=9V ~ 72V), pulse duty factor controls all the time between 15.3% ~ 42%.
As can be seen here, when compared with wide input voltage range, use second switch management and control transformer turns ratio, by arranging the input voltage threshold value of control turn ratio saltus step, the turn ratio of transformer secondary series connection winding, reduce the adjustable range of the pulse duty factor of described pwm control circuit, avoid circuit more greatly, comparatively work under small-pulse effect dutycycle time there is self-oscillation phenomenon, make feedback loop control more stable.That the input voltage range of Switching Power Supply can be done is wider, meets the application requirement of several functions.
Beneficial effect of the present invention:
The present invention casts aside the conventional method of original design isolated molded breadth input voltage range Switching Power Supply, adopt a kind of mentality of designing of novelty, utilize electronic switching circuit, the amplitude of variation of Switching Power Supply pulse duty factor is effectively reduced by the primary side number of turn adjusting switching mode power supply transformer in the course of the work, avoid circuit more greatly, work under the less limit dutycycle time there is self-oscillation phenomenon, circuit feedback loop is controlled more stable, improve the reliability of product.Simultaneously, use this technology, can when components and parts that circuit increases be less, Switching Power Supply can be made to realize on the original basis working in more wide input voltage range by design, and additional circuit can not produce extra noise, significantly impact is produced on other parameter of circuit.
The present invention, compared with adopting the Switching Power Supply of other conceptual design, has wide input voltage range, circuit is simple, Electro Magnetic Compatibility good, the feature such as shared volume is little, reliable and stable work.
Detailed description of the invention
Below in conjunction with accompanying drawing, the present invention is further detailed explanation.
As Fig. 1, a kind of Switching Power Supply by regulating the turn ratio to realize ultra-wide input voltage range shown in Fig. 2, it comprises the filter circuit 1 being connected to power supply input, input voltage monitoring and optoelectronic switch control circuit 3, the output of filter circuit 1 is connected with the primary side winding N1 of transformer B1, the output of filter circuit 1 is connected with pwm control circuit 2 by mu balanced circuit 4, pwm control circuit 2 is connected with feedback control loop 9, feedback control loop 9 is connected to the output of Switching Power Supply, input voltage monitoring and optoelectronic switch control circuit 3 comprise photoelectrical coupler IC4, the primary side winding N1 of transformer B1 is connected with the drain electrode of the first switch transistor T 1, the grid of the first switch transistor T 1 is connected with pwm control circuit 2 by switch tube driving circuit 5, the source electrode of the first switch transistor T 1 is connected with pwm control circuit 2 by current sampling circuit 6, the source electrode of the first switch transistor T 1 is connected with one end of the 4th resistor R4, the other end ground connection of the 4th resistor R4, the primary side of transformer B1 is by the second winding N2 tertiary winding N3 connected successively, 4th winding N4 forms, second winding N2 is connected with the output of Switching Power Supply by current rectifying and wave filtering circuit 8, one end of tertiary winding N3 is connected with current rectifying and wave filtering circuit 8, the other end is connected with turn ratio control circuit 7, 4th winding N4 is connected with photoelectrical coupler IC4 by turn ratio control circuit 7, input voltage monitoring and optoelectronic switch control circuit 3 pairs of input voltages detect in real time, input voltage and reference voltage are compared, and then control the switch of photoelectrical coupler IC4, make the second winding N2 of transformer B1 primary side, tertiary winding N3, 4th winding N4 forms different loops from turn ratio control circuit 7, by arranging the input voltage threshold value controlling turn ratio saltus step, change the turn ratio of transformer B1 primary side series connection winding, make the adjustable range of the pulse duty factor of pwm control circuit 2 in the reasonable scope, avoid Switching Power Supply and occur self-oscillation, make the control of feedback control loop more stable.
Filter circuit 1 is made up of the first electric capacity C1, the second electric capacity C2, the first inductor L1, the one termination power supply positive input terminal P1 of the first capacitor C1, another termination power supply negative input end P2, the one termination power supply positive input terminal P1 of the first inductor L1, No. 1 termination of the IN end of one end of another termination second capacitor C2, integrated regulator IC1 and the primary side winding N1 of the first transformer B1, another termination power supply ground terminal P2 of the second capacitor C2.Filter circuit 1 is bilateral network, has both prevented the AC influence composition inputted on electric wire from entering Switching Power Supply, suppresses high-frequency noise to produce harmful effect to Switching Power Supply; Prevent again the electromagnetic interference in Switching Power Supply from passing on electrical network by power line, electrical network is polluted.
Pwm control circuit 2 is made up of PWM control integration IC circuit 2, mu balanced circuit 4 is made up of integrated regulator IC1, the GND termination power supply ground terminal of integrated regulator IC1, the VCC end of OUT termination PWM control integration IC circuit 2 and 8 pin of voltage compare integrated circuit modules IC3; One end of the OUT termination first resistor R1 of PWM control integration IC circuit 2, one end of CS sampling termination the 3rd resistor R3 and the 3rd capacitor C3, GND termination power supply ground terminal, one end of first resistor R1 is connected with one end of the second resistor R2, the other end of the second resistor R2 is connected with the source electrode of the other end of the 3rd resistor R3, the first switch transistor T 1, another termination power supply ground terminal of the 3rd capacitor C3.The course of work of pwm control circuit 2 is: the output voltage signal monitored is sent into PWM control integration IC circuit 2 by feedback control loop 9, PWM control integration IC circuit 2 is to the real time signal processing collected, the driving pulse dutycycle of adjustment PWM pulse width modulator, thus reaching regulated output voltage object, integrated regulator IC1 is for PWM control integration IC circuit 2 provides stable operating voltage.
Input voltage monitoring and optoelectronic switch control circuit 3 are made up of voltage compare IC 3, photoelectrical coupler IC4, the 7th resistor R7, the 8th resistor R8, the 9th resistor R9, the tenth resistor R10, the 7th capacitor C7, the 5th diode D5, photoelectrical coupler IC4 inside comprises a light emitting diode and a phototriode, the one termination power supply positive input terminal P1 of the 7th resistor R7, one end of another termination the 8th resistor R8 and 3 pin of voltage compare IC 3; Another termination power supply ground terminal of 8th resistor R8; 2 pin of voltage compare IC 3 meet reference voltage P5, and 4 pin connect power supply ground terminal, and 8 pin connect the OUT end of integrated regulator IC1 and one end of the 7th capacitor C7, and 1 pin connects the anode of the 5th diode D5; Another termination of 7th capacitor C7 connects power supply ground terminal; The negative electrode of the 5th diode D5 connects one end of the 9th resistor R9; One end of another termination the tenth resistor R10 of 9th resistor R9 and 1 pin of photoelectrical coupler IC4; 2 pin of photoelectrical coupler IC4 connect the other end and the power supply ground terminal of the tenth resistor R10.The course of work of input voltage monitoring and optoelectronic switch control circuit 3 for: first at the input in the same way of voltage compare IC 3 by detecting in real time institute's input voltage, the voltage produced through the 7th resistor R7 sends into the voltage compare IC 3 be made up of operational amplifier, and compare with the reference voltage P5 being added in backward end, export from 1 pin of voltage compare IC 3 switch that low and high level controls photoelectrical coupler IC4; When input voltage is higher, the forward end voltage of voltage compare IC 3 is higher than backward end reference voltage, voltage compare IC 3 exports high level, makes the LEDs ON of photoelectrical coupler IC4 inside, simultaneously the triode ON of photoelectrical coupler IC4 inside; When input voltage is lower, the forward end voltage of voltage compare IC 3 is lower than backward end reference voltage, voltage compare IC 3 output low level, makes the light emitting diode not conducting of photoelectrical coupler IC4 inside, simultaneously the triode also not conducting of photoelectrical coupler IC4 inside.
Turn ratio control circuit 7, current rectifying and wave filtering circuit 8 constitute transformer B1 secondary-side control circuitry, current rectifying and wave filtering circuit 8 is made up of the first diode D1, the 4th capacitor R4, the 5th capacitor R5, the second inductor L2, turn ratio control circuit 7 is by second switch pipe T2, first Zener diode DZ1, second diode D2, 3rd diode D3, 4th diode D4, 5th resistor R5, 6th resistor R6, 6th capacitor R6 forms, and No. 3 terminations of the second winding N2 of transformer B1 meet Switching Power Supply negative output terminal P4 and the 4th capacitor C4, one end of 5th capacitor C5, No. 4 terminations of the second winding N2 connect the anode of the first diode D1 and No. 5 terminations of tertiary winding N3, and the negative electrode of the first diode D1 connects one end of the second inductor L2 simultaneously, the other end of the 4th capacitor C4, the negative electrode of the 4th diode D4, 3 pin of photoelectrical coupler IC4, the anode of the first Zener diode DZ1, one end of 6th resistor R6 and the 6th capacitor C6, the other end of another termination the 5th capacitor C5 of the second inductor L2 and Switching Power Supply positive output end P3, the source electrode of second switch pipe T2 connects the anode of the 4th diode D4, drain electrode connects the negative electrode of the second diode D2, and grid meets the 6th resistor R6, the other end of the 6th capacitor C6, the negative electrode of the first voltage-stabiliser tube DZ1,4 pin of photoelectrical coupler IC4 and one end of the 5th resistor R5, the negative electrode of another termination the 3rd diode D3 of the 5th resistor R5, the anode of the 3rd diode D3 connects No. 8 terminations of the 4th winding N4, No. 7 terminations of the 4th winding N4 connect the anode of the second diode D2 and No. 6 terminations of tertiary winding N3.Its course of work is: when input voltage is higher, voltage compare IC 3 exports high level, the light emitting diode of photoelectrical coupler IC4 inside, the equal conducting of triode, Voltage Establishment is not had between the grid of second switch pipe T2 and source electrode, second switch pipe T2 cannot conducting, in the loop that the tertiary winding N3 of transformer B1 is formed, no current flows through, the loop works that electric current is consisted of the second winding N2, the first diode D1 of transformer B1, the second inductor L2 and load, when input voltage is lower, voltage compare IC 3 output low level, the light emitting diode of photoelectrical coupler IC4 inside, triode all not conductings, the 4th winding N4 just by transformer B1 between the grid of second switch pipe T2 and source electrode, current rectifying and wave filtering circuit 8, mu balanced circuit 4 sets up suitable voltage, second switch pipe T2 conducting, now by the second winding N2 of transformer B1, tertiary winding N3, second diode D2, the voltage in the 4th diode D4 loop is higher than the second winding N2 by transformer B1, the voltage in the first diode D1 loop, first diode D1 is in reverse blocking state in whole loop, electric current is only by the second winding N2 of transformer B1, tertiary winding N3, second diode D2, 4th diode D4, the loop works that second inductor L2 and load are formed.
The present invention is a kind of technology utilizing the electronic switch control transformer turn ratio to realize Switching Power Supply ultra-wide input voltage range, pulse duty factor in circuit working is changed in more rational scope, thus realizes the object of ultra-wide input voltage range.
Technical scheme provided by the present invention; the circuit U CC2843 that just have been directed in field of switch power in inverse-excitation type wire topologies one comparatively general illustrates; this scheme directly can be replaced equally and is applied in other circuit structures; as in the circuit topological structure such as positive activation type, push-pull type; the concrete model of its circuit equally also has replaceability, should be considered as the protection domain of this patent.