CN217335453U

CN217335453U - Isolating switch power supply

Info

Publication number: CN217335453U
Application number: CN202221053088.XU
Authority: CN
Inventors: 李其军; 韦大纶; 骆威
Original assignee: Innolcon Medical Technology Suzhou Co Ltd
Current assignee: Innolcon Medical Technology Suzhou Co Ltd
Priority date: 2022-05-05
Filing date: 2022-05-05
Publication date: 2022-08-30
Anticipated expiration: 2032-05-05

Abstract

The utility model discloses an isolating switch power supply, which at least comprises a PFC power factor correction circuit, which is used for connecting a power grid and converting AC input output by the power grid into DC output; the LLC switching circuit is a high-voltage self-starting circuit comprising a multi-winding isolation transformer, converts the direct current output of the PFC power factor correction circuit into multi-path direct current voltage and supplies power to the PFC power factor correction circuit, the LLC switching circuit and a post-stage circuit. The isolating switch power supply of the scheme improves the power supply efficiency by using the power factor correction circuit, realizes the LLC switch circuit combining the wide voltage input of the power supply with the high-voltage self-starting form, does not need an external circuit to provide a direct-current power supply, simplifies the requirement on the external circuit, and simultaneously enables a rear-stage circuit to be isolated from a power grid by using the multi-winding isolating transformer in the LLC switch circuit, thereby realizing the power supply isolation output.

Description

Isolating switch power supply

Technical Field

The utility model belongs to the technical field of switching power supply and specifically relates to isolator power.

Background

A high-frequency electric knife (high-frequency surgical instrument) is an electric surgical instrument for replacing a mechanical surgical knife to cut tissues. The tissue is heated when the high-frequency high-voltage current generated by the tip of the effective electrode is contacted with the body, so that the separation and coagulation of the body tissue are realized, and the purposes of cutting and hemostasis are achieved. The electric energy that the electric wire netting was inserted needs just can act on the patient through corresponding handle through handling, and the mode that most often adopts is: the power grid is connected with alternating current and is converted into direct current through the power module, then the direct current is converted into high-frequency alternating current with specific frequency through the inverter circuit, and finally the high-frequency alternating current acts on a patient through handle output. The power supply module is used as a first link between a power grid and an output, is actually an energy source of the high-frequency electrotome, and is very important in design.

In the conventional switching power supply, the external power supply needs to be configured in the external circuit to provide the low voltage required by the normal operation of each circuit of the switching power supply, which makes the external circuit of the switching power supply relatively complex.

In addition, along with the increase of the application of the high-frequency electrotome in various operations, more and more various output modes, continuously increased output energy requirements, more severe safety requirements, higher requirements are provided for the design of a power supply module of the high-frequency electrotome: the power supply is safe, reliable, high in energy density, small in size, high in universality and simple to apply.

SUMMERY OF THE UTILITY MODEL

The utility model aims at providing an isolator power in order to solve the above-mentioned problem that exists among the prior art.

The purpose of the utility model is realized through the following technical scheme:

an isolated switching power supply includes

The PFC power factor correction circuit is used for connecting a power grid and converting alternating current input output by the power grid into direct current output;

the input end of the LLC switching circuit is connected with the output end of the PFC power factor correction circuit;

the LLC switching circuit is a high-voltage self-starting circuit comprising a multi-winding isolation transformer, converts the direct current output of the PFC power factor correction circuit into multi-path direct current voltage and provides low-voltage electric energy required by the work of the PFC power factor correction circuit, the LLC switching circuit and a post-stage circuit.

Preferably, an input end of a PFC control circuit of the PFC power factor correction circuit is connected to the input optical coupler isolation circuit and/or an output end of an output feedback circuit of the PFC power factor correction circuit is connected to the output optical coupler isolation circuit.

Preferably, the LLC switching circuit is a half-bridge LLC resonant switching circuit.

Preferably, the multi-winding isolation transformer comprises a primary winding, a first secondary winding, an auxiliary winding and a second secondary winding;

the primary winding is connected with a switch circuit in the LLC switch circuit, and the input end of the switch circuit is connected with the output end of the PFC power factor correction circuit and the output end of the LLC control circuit;

the first secondary winding is connected with the input end of a post-stage circuit and the feedback circuit of the LLC switch circuit through a first rectification loop, and the output end of the feedback circuit is connected with the input end of the LLC control circuit;

the auxiliary winding is at least connected with the PFC power factor correction circuit and an LLC control circuit of the LLC switch circuit through a second rectifying circuit and provides low-voltage electric energy required by the work of the PFC power factor correction circuit and the LLC control circuit;

and the second secondary winding is at least connected with a post-stage circuit through a third rectifying circuit and provides low-voltage electric energy required by the work of the post-stage circuit.

Preferably, the feedback circuit includes an output current feedback circuit, an input end of the output current feedback circuit is connected to an output end of the first rectification circuit, and an output end of the output current feedback circuit is connected to an input end of the LLC control circuit.

Preferably, the feedback circuit further comprises an overvoltage detection circuit and/or a first output voltage feedback circuit;

the input end of the overvoltage detection circuit is connected with the output end of the third rectifying circuit, and the output end of the overvoltage detection circuit is connected with the LLC control circuit;

the first output voltage feedback circuit is used for feeding back output voltage to an external circuit, and the input end of the first output voltage feedback circuit is connected with the output end of the first rectification loop.

Preferably, the output end of the first output voltage feedback circuit is connected with a first optical coupling isolation circuit;

and/or the enabling signal input end of the LLC control circuit is connected with a second optical coupling isolation circuit for electrically isolating the LLC control circuit from an external circuit.

Preferably, the post-stage circuit is a buck regulator circuit, and the buck regulator circuit is configured to adjust the first dc output of the LLC switch circuit to a desired dc voltage and output the dc voltage.

Preferably, the BUCK regulation circuit adopts an isolation synchronous rectification BUCK regulation circuit.

Preferably, the step-down regulating circuit comprises an upper MOS transistor, a lower MOS transistor, a first inductor, a freewheeling diode, an output filter capacitor, a second output voltage feedback circuit, an external control circuit, a feedback control circuit, and an isolation driving circuit; the drain electrode of the upper MOS tube is connected with the output end of the first rectifying loop of the LLC switching circuit, the source electrode of the upper MOS tube is connected with the drain electrode of the lower MOS tube, the negative electrode of the freewheeling diode and one end of the first inductor, the source electrode of the lower MOS tube and the anode of the freewheeling diode are grounded, the other end of the first inductor is grounded through an output filter capacitor and connected with the direct current regulation output end, the direct current regulation output end is connected with the second output voltage feedback circuit, the output end of the second output voltage feedback circuit is connected with the input end of the external control circuit, the output end of the external control circuit is connected with the input end of the feedback control circuit, the output end of the feedback control circuit is connected with the input end of the isolation driving circuit, and the output end of the isolation driving circuit is connected with the grids of the upper MOS tube and the lower MOS tube and controls the connection and disconnection of the upper MOS tube and the lower MOS tube.

Preferably, the step-down regulating circuit further comprises an overcurrent protection circuit for detecting at least whether the step-down regulating circuit has a short circuit or an abnormal current, and an output end of the overcurrent protection circuit is connected with the feedback control circuit through a third optocoupler isolation circuit.

The utility model discloses technical scheme's advantage mainly embodies:

the isolating switch power supply of the scheme improves the power supply efficiency by using the power factor correction circuit, realizes the LLC switch circuit combining the wide voltage input of the power supply with the high-voltage self-starting form, does not need an external circuit to provide a direct-current power supply, simplifies the requirement on the external circuit, and simultaneously enables a rear-stage circuit to be isolated from a power grid by using the multi-winding isolating transformer in the LLC switch circuit, thereby realizing the power supply isolation output.

The LLC switching circuit of this scheme is half-bridge LLC resonant switching circuit, and it is soft switching circuit, can adjust the output under the condition that input voltage and load change on a large scale, and switching frequency variation is very little relatively simultaneously, has improved power efficiency and density as far as possible, has effectively satisfied high frequency electrotome and has used in various operations.

The PFC power factor correction circuit and the LLC switch circuit can effectively realize electrical isolation with an external circuit through the optical coupling isolation circuit, so that the stability of structural use is ensured.

Each circuit of the scheme can effectively and timely process the abnormal condition in the power supply operation through the design of abnormal condition monitoring, feedback, overcurrent and overvoltage protection and the like, fully improves the safety of the power supply use, and is beneficial to prolonging the service life of equipment.

Drawings

Fig. 1 is a schematic diagram of an overall circuit structure of an isolation switching power supply of the present invention;

fig. 2 is a schematic circuit diagram of the PFC power factor correction circuit of the present invention;

fig. 3 is a schematic diagram of the main loop of the half-bridge LLC resonant switching circuit of the present invention;

fig. 4 is a schematic diagram of a feedback circuit and an LLC control circuit of the half-bridge LLC resonant switching circuit of the present invention;

fig. 5 is a schematic circuit diagram of the voltage-reducing regulating circuit of the present invention.

Detailed Description

Objects, advantages and features of the present invention will be illustrated and explained by the following non-limiting description of preferred embodiments. These embodiments are merely exemplary embodiments for applying the technical solutions of the present invention, and all technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the scope of the present invention.

In the description of the embodiments, it should be noted that the terms "center", "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description and simplicity of description, but do not indicate or imply that the devices or elements referred to must have a specific orientation, be constructed in a specific orientation, and be operated, and thus, should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. In the description of the embodiment, the operator is used as a reference, and the direction close to the operator is a proximal end, and the direction away from the operator is a distal end.

The isolation switch power supply disclosed by the present invention is explained below with reference to the accompanying drawings, and is mainly used for supplying power to the high-frequency electrotome, and of course, the isolation switch power supply can also be used in other application fields requiring the use of the switch power supply, and is not limited herein.

As shown in fig. 1, the isolated switching power supply includes a PFC power factor correction circuit 1, an LLC switching circuit 2, and a post-stage circuit.

The PFC power factor correction circuit 1 is used for connecting a power grid and converting alternating current input output by the power grid into direct current output; specifically, 85 Vac-265 Vac alternating current input of a power grid is converted into 390Vdc direct current output.

The LLC switch circuit 2 is connected with the dc output of the PFC power factor correction circuit 1,

The post-stage circuit is a voltage reduction regulating circuit 3, which is used for converting the first direct current output Hvdc of the LLC switch circuit 2 into required direct current voltage according to an external setting requirement and outputting the direct current voltage, and the adjustment range of the corresponding voltage value is between 0 and Hvdc.

As shown in fig. 2, the PFC power factor correction circuit 1 includes a full-wave rectifier bridge BD1, a boost inductor L1, a first diode D1, a MOS transistor Q1, an electrolytic capacitor C1, output voltage feedback resistors R1, R2, a current sampling resistor RISNS, a PFC control circuit 1-1, a power-on transient overshoot protection circuit 1-2, an overcurrent and overvoltage protection circuit 1-3, an input optical coupler isolation circuit, a first a/D conversion circuit 1-5, and an output optical coupler isolation circuit 1-6.

As shown in fig. 2, two cathodes and a positive connection point of four diodes of the full-wave rectifier bridge BD1 are connected to a power grid, the positive connection point of the two diodes is grounded through a current sampling resistor RISNS and connected to the PFC control circuit 1-1, the negative connection point of the two diodes is connected to one end of the boost inductor L1, the other end of the boost inductor L1 is connected to the positive electrode of the first diode D1 and the drain of the MOS transistor Q1, the negative electrode of the first diode D1 is connected to the dc output terminal and is grounded through an electrolytic capacitor C1, the source of the MOS transistor Q1 is grounded, the gate of the MOS transistor Q1 is connected to the PFC control circuit 1-1, one input end of the PFC control circuit 1-1 is connected to the output voltage feedback resistors R1 and R2, and the frequency of the Drive signal dr _ Q1 or the duty ratio of the Drive signal dr _ Q1 of the MOS transistor Q1 is controlled by a square wave according to the received input current signal ISNS and the output voltage feedback signal Vfb _ PFC 56, and finally the on-off control connection point of the MOS transistor Q1 is realized Thereby causing the dc output terminal to output 390V dc voltage. The utility model discloses in use UCC28180D as PFC control circuit's main control chip, adopt the regulation mode of fixed frequency change duty cycle, realize the follow of input current to voltage.

As shown in fig. 2, the electrolytic capacitor C1 is grounded through the power-on transient overshoot protection circuit 1-2, and the power-on transient overshoot protection circuit 1-2 is used to suppress the surge current at the moment of power-on to reduce the transient impact sustained by the device.

As shown in fig. 2, the dc output terminal is connected to the over-current over-voltage protection circuit 1-3, the over-current over-voltage protection circuit 1-3 is connected to the PFC control circuit 1-1, the over-current over-voltage protection circuit 1-3 is configured to generate an over-current protection signal OCP and an over-voltage protection signal OVP to the PFC control circuit 1 when determining that an abnormal state such as an over-current and an over-voltage occurs at an output of the PFC power factor correction circuit 1, and the PFC control circuit 1-1 actively stops working when determining that a fault occurs according to a received signal.

As shown in fig. 2, the first and second output voltage feedback resistors R1 and R2, the first a/D conversion circuit 1-5, and the output optical coupling isolation circuit 1-6 form an output feedback circuit to detect the output state of the PFC circuit 1. Output feedback signals Vfb _ PFC =390 × R2/(R1+ R2) of the first and second output voltage feedback resistors R1 and R2 are converted into corresponding digital signals by the first a/D conversion circuit 1-5, and are transmitted in an isolated manner by the output optical coupler isolation circuit 1-6.

And the output optical coupling isolation circuits 1-6 are connected with an external circuit. The external circuit can monitor the running state of the PFC power factor correction circuit 1 by reading the digital signal Vfb _ PFC _ D output by the output feedback circuit, and when the state is abnormal, the external circuit can actively change the enabling signal PFC _ EN of the PFC control circuit 1-1, so that the PEF power factor correction circuit 1 can be actively stopped. In addition, the enable signal PFC _ EN is transmitted to the PFC control circuit 1-1 in an isolation mode through the input optical coupling isolation circuit 1-4. The input optical coupling isolation circuits 1-4 and the output optical coupling circuits 1-6 realize the electrical isolation between an external circuit and the PFC power factor correction circuit 1.

As shown in fig. 1 and fig. 3, the LLC switch circuit 2 is a half-bridge LLC resonant switch circuit, and includes a switch circuit 2-3, a multi-winding isolation transformer T1, a first rectification circuit 2-5, a second rectification circuit 2-4, a third rectification circuit 2-6, a feedback circuit 2-2, and an LLC control circuit 2-1. The switching circuit 2-3, the multi-winding isolation transformer T1, the first rectifying circuit 2-5, the second rectifying circuit 2-4 and the third rectifying circuit 2-6 form a main circuit of the half-bridge LLC resonant switching circuit.

As shown in fig. 3, the switching circuit 2-3 includes a half-bridge upper MOS transistor Q2, a half-bridge lower MOS transistor Q3, a first resonant capacitor C2, a second resonant capacitor C3, and a resonant inductor L2. The drain electrode of the half-bridge upper MOS tube Q2 is connected with the direct current output end of the PFC power factor correction circuit 1 and is grounded through a first resonant capacitor C2 and a second resonant capacitor C3 which are connected in series, the source electrode of the half-bridge upper MOS tube Q2 is connected with the drain electrode of the half-bridge lower MOS tube Q3, and the source electrode of the half-bridge lower MOS tube Q3 is grounded. The source of the MOS tube Q2 on the half bridge is connected with one end of a primary winding Lp1 of the multi-winding isolation transformer T1, the other end of the primary winding Lp1 is connected with a connection point of the first resonant capacitor C2 and the second resonant capacitor C3 through the resonant inductor, and the resonant inductor L2, the first resonant capacitor C2 and the second resonant capacitor C3 and the primary winding Lp1 of the multi-winding isolation transformer T1 form a resonant network. And the gates of the upper MOS transistor Q2 and the lower MOS transistor Q3 of the half bridge are connected with the output end of the LLC control circuit 2-1.

As shown in fig. 1 and fig. 3, the multi-winding isolation transformer T1 further includes a first secondary winding Ls1, an auxiliary winding Lp2, and a second secondary winding Ls 2; the first secondary winding Ls1 is connected with a post-stage circuit and the feedback circuit 2-2 through a first rectifying loop 2-5, and the feedback circuit is connected with the LLC control circuit 2-1; the auxiliary winding Lp2 is connected with and supplies power to the PFC power factor correction circuit 1, the LLC control circuit 2-1 and a second optical coupling isolation circuit described below through a second rectifying loop 2-4; and the second secondary winding Lp2 is connected with and supplies power to the post-stage circuit, a second A/D conversion circuit in the LLC switching circuit and a first optical coupler isolation circuit through a third rectifying circuit 2-6.

As shown in fig. 3, the first rectifying circuit 2-5 includes a first rectifying bridge BD2 and a first electrolytic capacitor C4, and the first rectifying circuit 2-5 outputs a first dc output Hvdc to supply power to the following circuit. The second rectifying circuit 2-4 comprises a second rectifying bridge BD4 and a second electrolytic capacitor C6, and the second rectifying circuit 2-4 outputs a second direct current output Lvdc2 to provide voltage electric energy required by the work of all low-voltage power utilization modules (including a PLC control circuit, a first A/D conversion circuit, an output optical coupling isolation circuit, an input optical coupling isolation circuit and the like of the PFC power factor correction circuit 1), the LLC control circuit 2-1 and a second optical coupling isolation circuit described below of the PFC power factor correction circuit 1. The third rectifying circuit 2-6 comprises a third rectifying bridge BD3 and a third electrolytic capacitor C5, the third rectifying circuit 2-6 outputs a third direct current output Lvdc1, and the third direct current output Lvdc1 provides low-voltage electric energy required by the operation of all low-voltage electric modules (specifically, a feedback control circuit, a third optical coupling isolation circuit, a third a/D conversion circuit, a fourth optical coupling isolation circuit, an isolation driving circuit and the like in the voltage reduction regulating circuit described below) of the post-stage circuit and a second a/D conversion circuit and a first optical coupling isolation circuit described below in the LLC switch circuit 2.

When the half-bridge circuit works, the upper MOS tube Q2 and the lower MOS tube Q3 are switched on and off under the control of driving signals Drive _ Q2 and Drive _ Q3 of the LLC control circuit 2-1, direct current 390Vdc is converted into square waves with certain frequency and amplitude through a resonance network, the square waves are transmitted to an auxiliary winding Lp2, a first secondary winding Ls1 and a second secondary winding Ls2 through the magnetic field coupling of the multi-winding isolation transformer T1, and finally the square waves are transmitted to a first filter capacitor C4, a third filter capacitor C5 and a second filter capacitor BD 6 through the first rectifier bridge BD2, the third rectifier bridge BD3 and the BD4, and the second direct current output Lvdc2, the first direct current output Hvdc and the third direct current output Lvdc1 are output.

The feedback circuit 2-2 comprises an output current feedback circuit, an input end of the output current feedback circuit is connected with an output end of the first rectification circuit, and an output end of the output current feedback circuit is connected with an enable signal input end of the LLC control circuit.

As shown in fig. 3 and 4, the output current feedback circuit includes a current-limiting resistor R3, first and second voltage-dividing resistors R5, R6, a resistor R4, a TL431 controllable precision voltage regulator U1, and a photocoupler OPT 1.

During operation, a first direct current output Hvdc of the output of the first rectifying circuit is divided by the first voltage dividing resistor R5 and the second voltage dividing resistor R6 and then compared with a reference voltage of the TL431 controllable precision voltage-stabilizing source U1, and according to a comparison result, the change of the first direct current output Hvdc is switched to the change of a current Ifb flowing through the photocoupler OPT1 and sent to the LLC control circuit 2-1. The LLC control circuit 2-1 is composed of an LLC special control chip with a signal of UCC 256301. The LLC control circuit 2-1 adjusts the frequencies of driving signals Drive _ Q2 and Drive _ Q3 of the upper MOS tube Q2 and the lower MOS tube Q3 of the half bridge according to the change of the output feedback current Ifb, so as to realize the stable control of the first direct current output Hvdc. The LLC control circuit 2-1 detects the current Ic3 flowing through the resonant capacitor C3 at the same time, and overcurrent protection of the circuit is achieved.

The feedback circuit 2-2 further comprises an overvoltage detection circuit, an input end of the overvoltage detection circuit is connected with an output end of the third rectification circuit 2-6, and an output end of the overvoltage detection circuit is connected with an input end of the LLC control circuit 2-1.

As shown in fig. 3 and fig. 4, the overvoltage detection circuit includes a third voltage dividing resistor R9 and a fourth voltage dividing resistor R10 connected in series, the voltage dividing resistor R9 is connected to the output terminal of the third rectifying circuit 2-6, and the connection point of the third voltage dividing resistor R9 and the third voltage dividing resistor R10 is connected to the input terminal of the LLC control circuit 2-1. During working, a third direct current output LVDC1 output by the third rectifying circuit 2-6 generates an overvoltage protection signal OVP through a third voltage dividing resistor R9 and a fourth voltage dividing resistor R10 and sends the overvoltage protection signal OVP to the LLC control circuit 2-1, and the LLC control circuit 2-1 actively stops working when determining that an overvoltage fault occurs according to the overvoltage protection signal OVP.

The feedback circuit 2-2 further comprises a first output voltage feedback circuit for feeding back an output voltage to an external circuit, an input end of the first output voltage feedback circuit is connected with an output end of the first rectification circuit, and an output end of the first output voltage feedback circuit is connected with a first optical coupling isolation circuit.

As shown in fig. 3 and fig. 4, the first output voltage feedback circuit includes a fifth voltage dividing resistor R7, a sixth voltage dividing resistor R8, a second a/D conversion circuit 2-8, and a first optical coupler isolation circuit 2-9 connected in series. The fifth voltage-dividing resistor R7 is connected with the output end of the first rectifying loop, the connection point of the fifth voltage-dividing resistor R7 and the sixth voltage-dividing resistor R8 is connected with the second A/D conversion circuit 2-8, the second A/D conversion circuit 2-8 is connected with the first optical coupling isolation circuit 2-9, and the first optical coupling isolation circuit 2-9 is connected with an external circuit.

When the circuit works, the first direct current output Hvdc of the first rectifying circuit 2-5 generates an output voltage feedback signal Vfb _ LLC through the fifth voltage dividing resistor R7 and the sixth voltage dividing resistor R8, the output voltage feedback signal Vfb _ LLC =390 × R7/(R7+ R8), the analog level signal is converted into a corresponding digital signal through the A/D conversion circuit 2-8, isolated transmission is realized through the optical coupling isolation circuit 2-9, an external circuit can monitor the running state of the LLC switch circuit 2 by reading the digital signal Vfb _ LLC _ D, and when the running state is determined to be abnormal, the enabling signal LLC _ EN of the LLC control circuit 2-1 can be actively changed to actively stop working. The enable signal LLC _ EN is transmitted to the LLC control circuit 2-1 in an isolated manner via a second optical coupler isolation circuit 2-7. The first optical coupling isolation circuit 2-9 and the second optical coupling isolation circuit 2-7 realize the electrical isolation of the external circuit and the LLC switch circuit 2.

As shown in fig. 5, the BUCK regulation circuit 3 employs an isolated synchronous rectification BUCK regulation circuit. The voltage reduction regulating circuit 3 comprises an upper MOS tube Q4, a lower MOS tube Q5, a first inductor L3, a freewheeling diode D2, an output filter capacitor C7, a second output voltage feedback circuit, an external control circuit 3-5, a feedback control circuit 3-4 and an isolation driving circuit 3-1; the drain of the upper MOS tube Q4 is connected with the output end of a first rectification loop 2-5 of the LLC switch circuit 2, the source of the upper MOS tube Q4 is connected with the drain of a lower MOS tube Q5, the negative electrode of a freewheeling diode D2 and one end of a first inductor L3, the source of the lower MOS tube Q5 and the positive electrode of a freewheeling diode D2 are grounded, the other end of the first inductor L3 is grounded through an output filter capacitor C7 and connected with a direct current regulation output end, the direct current regulation output end is connected with the second output voltage feedback circuit, the output end of the second output voltage feedback circuit is connected with the input end of the external control circuit 3-5, the output end of the external control circuit 3-5 is connected with the input end of the feedback control circuit 3-4, the output end of the feedback control circuit 3-4 is connected with the input end of an isolation drive circuit 3-1, the output end of the isolation driving circuit 3-1 is connected with the gates of the upper MOS transistor Q4 and the lower MOS transistor Q5 and controls the on-off of the upper MOS transistor Q4 and the lower MOS transistor Q5.

In operation, the external control circuit 3-5 sends an output level setting signal Vset to the feedback control circuit 3-4 according to the requirement, and the feedback control circuit 3-4 outputs PWM signals PWM _ Q4 and PWM _ Q5 with specific duty ratio according to Vset. The isolation driving circuit 3-1 generates actual driving signals Drive _ Q4 and Drive _ Q5 according to the received driving signals PWM _ Q4 and PWM _ Q5, so as to realize the high-voltage side driving of the upper MOS transistor Q4, and the isolation driving circuit 3-1 realizes the isolation of the feedback control circuit 3-4 from the upper and lower MOS transistors Q4 and Q5.

As shown in fig. 5, the feedback control circuit 3-4 is mainly composed of a UC3824 chip, the output dc voltage Vout generates an output feedback voltage Vfb through seventh and eighth voltage dividing resistors R11 and R12, the output feedback voltage Vfb passes through a third a/D conversion circuit 3-2, the analog quantity Vfb is converted into a digital signal Vfb _ D, the digital signal Vfb _ D is connected to an external control circuit 3-5 through a fourth opto-isolator circuit 3-3, the seventh and eighth voltage dividing resistors R11, R12 and the third a/D conversion circuit 3-2 form the second output voltage feedback circuit, the external control circuit 3-5 converts the output voltage feedback digital signal Vfb _ D into an analog signal Vfb1, and outputs the analog signal Vfb1 to the feedback control circuit 3-4, the feedback control circuit 3-4 performs negative feedback control, thereby realizing the Vset following by the output Vout, and simultaneously, the fourth optical coupling isolation circuit realizes the isolation of the feedback control circuit 3-4 from the output direct current voltage Vout.

As shown in the attached figure 5, the external control circuit 3-5 can be decided by the actual use condition as the intermediate link of the closed loop feedback of the voltage reduction regulating circuit 3, the utility model discloses do not design, only need according to the utility model discloses the regulation provide corresponding signal interface can. When the step-down regulating circuit 3 needs to be operated, the external control circuit 3-5 sets the enable signal BUCK _ EN to be in a working state, and then the operation can be started. The specific structures of the feedback control circuit 3-4 and the isolation driving circuit 3-1 are also known in the art, and are not limited herein.

As shown in fig. 5, the buck regulating circuit 3 further includes an overcurrent protection circuit for detecting at least whether the buck regulating circuit 3 has a short circuit or an abnormal current, the overcurrent protection circuit 3-7 is connected between the voltage dividing resistor R12 and the ground GND1, and an output end of the overcurrent protection circuit 3-7 is connected to the feedback control circuit 3-4 through a third optical coupling isolation circuit 3-6. The over-current protection circuit 3-7 detects whether the voltage reduction regulating circuit 3 has short circuit and current abnormal conditions, an over-current protection signal OCP _ ISO is transmitted to the feedback control circuit 3-4 through the third optical coupling isolation circuit 3-6, the feedback control circuit 3-4 monitors the OCP state in real time, and the circuit is actively stopped when the over-current state occurs.

The utility model has a plurality of implementation modes, and all technical schemes formed by adopting equivalent transformation or equivalent transformation all fall within the protection scope of the utility model.

Claims

1. An isolated switching power supply includes

the method is characterized in that:

the LLC switch circuit is a high-voltage self-starting circuit comprising a multi-winding isolation transformer, converts the direct current output of the PFC power factor correction circuit into multi-path direct current voltage and provides low-voltage electric energy required by the work of the PFC power factor correction circuit, the LLC switch circuit and a post-stage circuit.

2. The isolated switching power supply of claim 1, wherein: the input end of a PFC control circuit of the PFC power factor correction circuit is connected with an input optical coupling isolation circuit and/or the output end of an output feedback circuit of the PFC power factor correction circuit is connected with an output optical coupling isolation circuit.

3. The isolated switching power supply of claim 1, wherein: the LLC switching circuit is a half-bridge LLC resonant switching circuit.

4. The isolated switching power supply of claim 1, wherein: the multi-winding isolation transformer comprises a primary winding, a first secondary winding, an auxiliary winding and a second secondary winding;

5. The isolated switching power supply of claim 4, wherein: the feedback circuit comprises an output current feedback circuit, the input end of the output current feedback circuit is connected with the output end of the first rectifying circuit, and the output end of the output current feedback circuit is connected with the input end of the LLC control circuit.

6. The isolated switching power supply of claim 5, wherein: the feedback circuit further comprises an overvoltage detection circuit and/or a first output voltage feedback circuit;

the first output voltage feedback circuit is used for feeding back output voltage to an external circuit, and the input end of the first output voltage feedback circuit is connected with the output end of the first rectifying loop.

7. The isolated switching power supply of claim 6, wherein:

the output end of the first output voltage feedback circuit is connected with a first optical coupling isolation circuit;

and/or an enabling signal input end of the LLC control circuit is connected with a second optical coupling isolation circuit for electrically isolating the LLC control circuit from an external circuit.

8. An isolated switching power supply according to any one of claims 1 to 7, wherein: the post-stage circuit is a voltage reduction regulating circuit, and the voltage reduction regulating circuit is used for regulating the first direct current output of the LLC switching circuit into required direct current voltage and outputting the direct current voltage.

9. The isolated switching power supply of claim 8, wherein: the step-down regulating circuit adopts an isolation synchronous rectification BUCK step-down regulating circuit.

10. The isolated switching power supply of claim 8, wherein: the voltage reduction regulating circuit comprises an upper MOS tube, a lower MOS tube, a first inductor, a freewheeling diode, an output filter capacitor, a second output voltage feedback circuit, an external control circuit, a feedback control circuit and an isolation drive circuit; the drain electrode of the upper MOS tube is connected with the output end of the first rectifying loop of the LLC switching circuit, the source electrode of the upper MOS tube is connected with the drain electrode of the lower MOS tube, the negative electrode of the freewheeling diode and one end of the first inductor, the source electrode of the lower MOS tube and the anode of the freewheeling diode are grounded, the other end of the first inductor is grounded through an output filter capacitor and is connected with the direct current regulation output end, the output end of the direct current regulation output end is connected with the second output voltage feedback circuit, the output end of the second output voltage feedback circuit is connected with the input end of the external control circuit, the output end of the external control circuit is connected with the input end of the feedback control circuit, the output end of the feedback control circuit is connected with the input end of the isolation driving circuit, and the output end of the isolation driving circuit is connected with the grids of the upper MOS tube and the lower MOS tube and controls the connection and disconnection of the upper MOS tube and the lower MOS tube.

11. The isolated switching power supply of claim 10, wherein: the step-down regulating circuit further comprises an overcurrent protection circuit for at least detecting whether the step-down regulating circuit has short circuit and abnormal current, and the output end of the overcurrent protection circuit is connected with the feedback control circuit through a third optical coupling isolation circuit.