CN112087145A - Isolation DC-DC circuit applied to electric power product - Google Patents
Isolation DC-DC circuit applied to electric power product Download PDFInfo
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- CN112087145A CN112087145A CN202010934306.XA CN202010934306A CN112087145A CN 112087145 A CN112087145 A CN 112087145A CN 202010934306 A CN202010934306 A CN 202010934306A CN 112087145 A CN112087145 A CN 112087145A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
- H02M1/34—Snubber circuits
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0038—Circuits or arrangements for suppressing, e.g. by masking incorrect turn-on or turn-off signals, e.g. due to current spikes in current mode control
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The invention discloses an isolated DC-DC circuit applied to an electric power product, which comprises: and the input voltage and linear voltage stabilizing module is used for performing voltage stabilizing control on the voltage with unstable input. And the undervoltage protection module monitors the input voltage through the sampling resistor to enable the control chip. The transformer comprises a primary coil and a secondary coil, and the primary coil is connected with the voltage input and the switching tube; the secondary coil is connected with the output module. And the buffer module is used for absorbing the peak generated at the turn-off moment of the switching tube. The control module U1 is used for controlling the on-off of the primary coil, and when the control module controls the primary coil to be connected with the input voltage, the input voltage excites the primary coil and stores the energy in the form of magnetic energy; when the control module controls the primary coil to be disconnected, the primary coil transfers energy to the secondary coil to generate the working voltage required by the load. The switch tube is connected between the primary coil and the control module, and the external switch tube can improve the output voltage range of the Boost chip. And the feedback module is used for sampling the change of the output voltage and generating a feedback signal according to the sampled output voltage signal. The boost flyback circuit can improve the power conversion efficiency and is suitable for low-voltage input occasions.
Description
Technical Field
The invention belongs to the technical field of switching power supplies, and particularly relates to an isolated DC-DC circuit applied to an electric power product.
Background
The flyback circuit, as an isolated DC-DC circuit, has the advantages of high reliability, low cost, simple design and the like, and is widely applied to various electric power products. In power products, various different level requirements are often met, and because the operating voltages of all parts are different and independent, multiple level conversions are sometimes needed to be carried out, and an isolated DC-DC circuit is designed.
The flyback type is that when the power MOSFET is switched on, electric energy is stored on a primary coil of the high-frequency transformer, and only when the MOSFET is switched off, the electric energy is transmitted to a secondary coil, so that the high-frequency transformer can rapidly store and release energy due to high switching frequency, and direct-current continuous output can be obtained after high-frequency rectification and filtering. And the feedback loop regulates the duty ratio by controlling the current of the control end of the TOPSwitch device so as to achieve the purpose of voltage stabilization. The working voltage of a common flyback control chip is basically over 10V, so that the working voltage of the common flyback control chip cannot meet the low-voltage requirement on the occasion of low-voltage input, and the DC-DC chip cannot meet the isolation requirement when being used alone.
The invention uses the Boost chip as the main control chip of the isolated DC-DC circuit, realizes the level conversion in the low-voltage input occasion, and well solves the requirement that the electric power product needs to carry out multiple isolated level conversions.
Disclosure of Invention
In order to solve the defects of the prior art, the invention aims to provide an isolated DC-DC circuit applied to an electric power product, which utilizes the low working voltage of a Boost chip and the characteristics of a flyback circuit as a main control chip, utilizes a flyback transformer as a topological inductor of the Boost circuit, can meet the requirement of the Boost circuit on inductor energy storage and realize isolation, utilizes an error amplifier in the Boost chip to realize the regulation of a driving duty ratio, amplifies the difference value of a feedback voltage (FB pin voltage) and a reference voltage, and then controls the duty ratio of a PWM output signal by using the signal. The invention combines the Boost chip and the flyback circuit to realize level conversion in low-voltage input occasions, thereby solving the requirement that electric power products need to carry out multiple isolated level conversion.
To achieve the above object, the present invention provides an isolated DC-DC circuit applied to an electric power product, comprising: the circuit comprises an input voltage, a linear voltage stabilizing module, an under-voltage protection module, a buffer module, a control module U1, a transformer, a switch tube VT2, a feedback module and a voltage output module.
And the linear voltage stabilizing module is used for converting the input voltage into the set stable direct-current voltage and performing voltage stabilizing control on the unstable voltage so as to provide power supply voltage for the control module U1 and provide driving voltage for the switching tube. The module comprises a resistor R3, a voltage regulator tube VD1, a triode VT1 and a capacitor C3, wherein the resistor R3 and the voltage regulator tube VD1 are connected in series and are connected between an input voltage VIN and GND, the base electrode of the triode VT1 is connected with the lower end of the resistor R3, the collector electrode of the triode is connected with the input voltage VIN, the emitter electrode of the triode is connected with the upper end of the capacitor C3, and the lower end of the capacitor C3 is connected with GND.
The undervoltage protection module is used for monitoring the change of input voltage, when the output voltage is above the set voltage, the control chip enables, the whole circuit is in an activated state, when the input voltage is above the set voltage, the control module U1 is closed, the whole circuit is in a closed state, and the components and parts in the circuit are prevented from being damaged under the condition of low-voltage large current. The undervoltage protection module comprises resistors R1 and R2, the resistors R1 and R2 are connected in series and are connected between an input voltage VIN and GND, and the upper end of the resistor R2 is connected with an EN pin of the control chip.
The buffer module is used for absorbing a peak generated at the moment of turning off the switching tube, when the switching tube VT2 is turned off, the primary coil of the transformer is disconnected from the input voltage, a voltage peak can be generated in the primary coil of the transformer, and the voltage peak charges the capacitor C2 through the resistor R4 of the buffer module, so that the voltage peak is absorbed, and the voltage peak is prevented from damaging the switching tube VT 2; the buffer module comprises a resistor R4 and a capacitor C2, wherein the resistor R4 and the capacitor C2 are connected in series and are connected to the primary coil of the transformer.
The control module U1 is connected to the switching tube VT2, and is configured to control the switching tube VT2 to turn on and off the transformer.
The switch tube VT2 is an N-channel MOS tube and is connected between the primary coil of the transformer and the control module, and the external switch tube VT2 can improve the output voltage range of the Boost chip.
The transformer comprises a primary coil and a secondary coil, wherein the primary coil is connected to an input voltage and a switching tube VT2, and the secondary coil is connected with the output module through a connecting diode VD 3; when the switching tube VT2 is conducted, the primary coil is connected with the input voltage, the input voltage excites the primary coil and stores the energy in the form of magnetic energy; when the switching tube VT2 is turned off, the primary coil is disconnected from the input voltage, and the primary coil transfers energy to the secondary coil to generate the operating voltage required by the load.
The feedback module is used for sampling the change of the output voltage and generating a feedback signal according to the sampled output voltage signal; when the primary coil of the transformer is switched on, the control module adjusts the duty ratio of a signal provided to the source electrode of the switching tube VT2 according to the feedback signal of the feedback module, so as to adjust the working voltage required by the output load. The module comprises resistors R5, R6, R7, R8, R9, a photoelectric coupler O1 and a reference voltage source VD2, wherein the resistors R8 and R9 are connected in series and are connected between an output voltage Vo and GND, and the upper end of the resistor R9 is connected with the reference end of the reference voltage source VD 2; the cathode of a reference voltage source VD2 is connected with the cathode of the primary LED of the optical coupler, the lower end of a resistor R7 is connected with the anode of the LED of the optical coupler, and the upper end of the resistor R7 is connected with output voltage; the resistors R5 and R6 are connected in series and connected between the power supply voltages VCC and PGND, the collector of the optocoupler secondary triode is connected with the upper end of the resistor R5, and the emitter of the optocoupler secondary triode is connected with the lower end of the resistor R5 and the FB pin of the chip of the control module U1.
The voltage output module is connected with the secondary coil of the transformer.
The invention has the beneficial effects that:
1. the structure is simple, the cost is low, and the level conversion requirement of the electric power product during low-voltage input can be effectively met;
2. the output voltage range of the Boost chip is expanded, and higher voltage conversion ratio can be realized.
Drawings
Fig. 1 is a block diagram of a circuit structure of an isolated DC-DC circuit applied to an electric power product according to the present invention.
Fig. 2 is a circuit schematic of an isolated DC-DC circuit of the present invention applied to an electrical product.
Detailed Description
The invention is described below with reference to the accompanying drawings:
as shown in fig. 1, the isolated DC-DC circuit applied to an electric power product of the present invention includes an input voltage, a voltage stabilizing module, an under-voltage protection module, a buffer module, a control module U1, a transformer, a switching tube VT2, a feedback module, and a voltage output module.
Fig. 2 is a diagram of an isolated DC-DC circuit of the present invention applied to an electrical product.
The input capacitor C1 filters the input voltage. The voltage stabilizing module comprises a resistor R3, a voltage stabilizing tube VD1 and a triode VT1, and is used for converting input voltage into set stable direct current voltage so as to provide power supply voltage for the control module U1 and drive voltage for the switching tube VT 2. The transformer includes a primary coil and a secondary coil. The primary coil is connected to an input voltage and the switching tube VT2 and used for receiving the input voltage to store energy when the switching tube VT2 is conducted, the secondary coil converts the energy stored when the primary coil is conducted into an operating voltage required by the voltage output module when the switching tube VT2 is disconnected, and the voltage output module is connected to the secondary coil. The switching transistor VT2 is an N-channel MOS transistor. The control module U1 is a Boost chip, and is connected to the switching tube VT2, and is used for controlling the switching tube VT2 to turn on and off to realize the control of turning on and off the transformer. The buffer module comprises a resistor R4 and a capacitor C2. When the switching tube VT2 is turned off, the first primary winding of the transformer is disconnected from the input voltage, and a voltage spike is generated in the primary winding of the transformer, and the voltage spike charges the capacitor C2 through the resistor R4, so that the voltage spike is absorbed and prevented from damaging the switching tube VT 2. The undervoltage protection module comprises resistors R1 and R2, undervoltage protection is used for monitoring the change of input voltage, when the output voltage is above the set voltage, the control module U1 is enabled, the whole circuit is in an activated state, when the input voltage is above the set voltage, the control module U1 is closed, the whole circuit is in a closed state, and the damage to components in the circuit caused by the low-voltage high-current condition is prevented. The feedback module comprises resistors R5, R6, R7, R8, R9, a photoelectric coupler O1 and a reference voltage source VD 2. The feedback module is used for sampling the change of the output voltage and generating a feedback signal according to the sampled output voltage signal. The output voltage block comprises a diode VD3 and a capacitor C4. When the switching tube VT2 is turned on, the primary coil of the transformer is connected to the input voltage, and the control module U1 adjusts the duty ratio of the signal provided to the source of the switching tube according to the feedback signal of the feedback module, thereby adjusting the operating voltage required by the output load.
In this embodiment, when the switching tube VT2 is turned off, the primary winding may generate a voltage spike due to the leakage inductance of the transformer, and the voltage spike may damage the switching tube, so that the buffer module is utilized to absorb the voltage spike of the switching tube when the first primary winding is turned off, thereby preventing the voltage spike from damaging the switching tube. In another embodiment of the present invention, the voltage spike generated when the switching tube VT2 is turned off is not absorbed, and therefore, the buffer module may not be provided.
In this embodiment, when the switching transistor VT2 is connected to the driving pin of the control module U1 and the primary coil of the transformer, the switching transistor is used to share a part of the voltage spike stress generated by the primary coil when the driving chip is turned off, so as to improve the voltage endurance of the control module U1. When the required output voltage is small or the reflected voltage of the secondary side of the transformer is small, the upper limit of the withstand voltage of the control module U1 is not reached, the switching tube VT2 may not be provided.
In the present embodiment, a linear voltage regulation module is provided to regulate the variation of the input voltage so as to provide a stable operating voltage for the control module U1 and a stable driving voltage for the switching tube. If the input voltage is stable and within the required voltage range, the linear voltage stabilizing module is not needed.
Referring to fig. 2, the voltage converting module is a linear voltage stabilizing module, but the present invention is not limited thereto. The voltage conversion module is connected to the control module U1 and the gate of the switching tube to provide a stable operating voltage and driving voltage for the switching tube.
In summary, the flyback circuit according to the embodiment of the present invention utilizes the characteristic of low operating voltage of the Boost chip to complement the advantages of the flyback circuit, thereby solving the problem of level conversion under the condition of low voltage input.
The above description is only an example of the present invention and should not be construed as limiting the scope of the present invention, and any modifications, equivalent replacements, improvements, etc. within the scope of the present invention and the contents of the accompanying drawings should be included in the protection scope of the present invention.
Claims (8)
1. An isolated DC-DC circuit for application to an electrical product, comprising: input voltage, linear voltage regulation module, undervoltage protection module, buffer module, control module U1, transformer, switch tube VT2, feedback module and voltage output module, its characterized in that:
the linear voltage-stabilizing module comprises a resistor R3, a voltage-stabilizing tube VD1, a triode VT1 and a capacitor C3, wherein the resistor R3 and the voltage-stabilizing tube VD1 are connected in series and are connected between an input voltage VIN and GND, the base electrode of the triode VT1 is connected with the lower end of the resistor R3, the collector electrode of the triode VT1 is connected with the input voltage VIN, the emitter electrode of the triode VT1 is connected with the upper end of the capacitor C3, and the lower end of the C3 is connected with;
the undervoltage protection module comprises resistors R1 and R2, the resistors R1 and R2 are connected in series and are connected between an input voltage VIN and GND, and the upper end of the resistor R2 is connected with an EN pin of the control module U1;
the buffer module comprises a resistor R4 and a capacitor C2, wherein the resistor R4 and the capacitor C2 are connected in series and are connected to the primary coil of the transformer in parallel;
the control module U1 is connected with the switching tube VT2 and is used for controlling the switching tube VT2 to be switched on and off so as to realize the on and off of the primary coil of the transformer;
the switching tube VT2 is connected between the primary coil of the transformer and the control module U1;
the transformer comprises a primary coil and a secondary coil, wherein the primary coil is connected to an input voltage and a switching tube VT2, and the secondary coil is connected with the output module through a connecting diode VD 3;
the voltage output module is connected to a secondary coil of the transformer;
the feedback module comprises resistors R5, R6, R7, R8, R9, a photoelectric coupler O1 and a reference voltage source VD 2; the resistors R8 and R9 are connected in series and are connected between the output voltage Vo and GND, and the upper end of the resistor R9 is connected with the reference end of the reference voltage source VD 2; the cathode of a reference voltage source VD2 is connected with the cathode of the primary LED of the optical coupler, the lower end of a resistor R7 is connected with the anode of the LED of the optical coupler, and the upper end of the resistor R7 is connected with output voltage; the resistors R5 and R6 are connected in series and connected between the power supply voltages VCC and PGND, the collector of the optocoupler secondary triode is connected with the upper end of the resistor R5, and the emitter of the optocoupler secondary triode is connected with the lower end of the resistor R5 and the FB pin of the chip of the control module U1.
2. The isolated DC-DC circuit of claim 1, wherein the linear regulator module is configured to convert the input voltage into a stable DC voltage, so as to provide a supply voltage for the control module and a driving voltage for the switching transistor VT 2.
3. The isolated DC-DC circuit applied to power products of claim 1, wherein the primary winding of the transformer is used for receiving an input voltage to store energy when a switching tube VT2 is turned on; the secondary coil of the transformer converts the energy stored when the primary coil is turned on into the working voltage required by the voltage output module when the switching tube VT2 is turned off.
4. An isolated DC-DC circuit applied to power products as claimed in claims 1 and 3, wherein the switch VT2 is an N-channel MOS transistor.
5. The isolated DC-DC circuit applied to power products of claim 1, wherein the control module U1 is used for controlling the switch tube VT2 to be turned on and off.
6. The isolated DC-DC circuit applied to power products of claim 1, wherein the snubber module is used to prevent voltage spike from damaging the VT2, when the VT2 is turned off, the primary winding of the transformer is disconnected from the input voltage, and voltage spike is generated in the primary winding of the transformer, and the voltage spike charges the capacitor C2 through the resistor R4 of the snubber module, so as to absorb the voltage spike and prevent the voltage spike from damaging the VT 2.
7. The isolated DC-DC circuit applied to the electric power product of claim 1, wherein the undervoltage protection module is used for monitoring the variation of the input voltage, when the output voltage is above the set voltage, the control module U1 is enabled, the whole circuit is in an active state, when the input voltage is above the set voltage, the control module U1 is turned off, the whole circuit is in an off state, and the components in the circuit are prevented from being damaged due to the occurrence of a low-voltage large-current condition.
8. The isolated DC-DC circuit applied to an electric power product of claim 1, wherein the feedback module is configured to sample the variation of the output voltage and generate a feedback signal according to the sampled output voltage signal; when the primary coil of the transformer is switched on, the control module adjusts the duty ratio of a signal provided to the source electrode of the switching tube VT2 according to the feedback signal of the feedback module, so as to adjust the working voltage required by the output load.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010934306.XA CN112087145A (en) | 2020-09-07 | 2020-09-07 | Isolation DC-DC circuit applied to electric power product |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202010934306.XA CN112087145A (en) | 2020-09-07 | 2020-09-07 | Isolation DC-DC circuit applied to electric power product |
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| Publication Number | Publication Date |
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| CN112087145A true CN112087145A (en) | 2020-12-15 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202010934306.XA Pending CN112087145A (en) | 2020-09-07 | 2020-09-07 | Isolation DC-DC circuit applied to electric power product |
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Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102036450A (en) * | 2010-12-13 | 2011-04-27 | 成都成电硅海科技股份有限公司 | LED driving circuit |
| CN202455269U (en) * | 2011-10-20 | 2012-09-26 | 四川长虹电器股份有限公司 | Switch power supply with standby switching circuit |
| CN102662424B (en) * | 2012-03-23 | 2014-12-03 | 上海信耀电子有限公司 | Precise voltage stabilizing circuit for singlechip |
-
2020
- 2020-09-07 CN CN202010934306.XA patent/CN112087145A/en active Pending
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102036450A (en) * | 2010-12-13 | 2011-04-27 | 成都成电硅海科技股份有限公司 | LED driving circuit |
| CN202455269U (en) * | 2011-10-20 | 2012-09-26 | 四川长虹电器股份有限公司 | Switch power supply with standby switching circuit |
| CN102662424B (en) * | 2012-03-23 | 2014-12-03 | 上海信耀电子有限公司 | Precise voltage stabilizing circuit for singlechip |
Non-Patent Citations (2)
| Title |
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| TI工程师: "《LM5022技术手册》", 31 December 2017 * |
| 胡存生: "《集成开关电源的设计制作调试与维修》", 30 April 1995 * |
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Application publication date: 20201215 |