CN218783723U - Flyback switching power supply based on control chip - Google Patents
Flyback switching power supply based on control chip Download PDFInfo
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- CN218783723U CN218783723U CN202222759690.1U CN202222759690U CN218783723U CN 218783723 U CN218783723 U CN 218783723U CN 202222759690 U CN202222759690 U CN 202222759690U CN 218783723 U CN218783723 U CN 218783723U
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
A single-ended DC-DC flyback switching voltage-stabilized power supply based on a control chip is disclosed, in order to solve the problem of insufficient driving peak current, the method that an auxiliary driving circuit is arranged between the output end of the control chip and the input end of an MOS (metal oxide semiconductor) tube is adopted in the invention, so that the problem of insufficient driving peak current is solved, the MOS switching tube can be quickly switched on, and the high-frequency oscillation of a rising edge is avoided; meanwhile, a path with low impedance as far as possible is provided at the moment of MOS turn-off, and the voltage of a capacitor between the grid and the source of the MOS tube is quickly released, so that the switching tube can be quickly turned off, the turn-off time is shortened, the loss during turn-off is reduced, and the phenomenon that the current is too large during turn-off to burn off a power supply IC is avoided. The flyback switching power supply has the advantages of simplicity and convenience in installation and debugging, excellent performance and the like due to the modular design, and is suitable for a 20W-40W small-sized power switching power supply.
Description
Technical Field
The invention relates to the technical field of power supplies, in particular to a flyback switching power supply based on a control chip.
Background
In recent years, the application range of the switching power supply is wider and wider, and the switching power supply has the advantages of small volume, light weight, high efficiency, stability and convenience in use and maintenance, and gradually replaces the traditional linear voltage-stabilized power supply. At present, an 18V-36V input power supply is mostly adopted in a low-voltage input power supply system, and a secondary power supply converts input direct-current voltage into direct-current voltage which is more stable, has small ripples and is more enhanced in loading capacity through various modes such as boosting, reducing, isolating, non-isolating and the like, so as to provide continuous electricity for different functional components. And then the power utilization rate is improved, and the electric energy loss is reduced. The switching power supply is widely applied to the fields of communication, aerospace, industrial automation, instruments and meters, automobiles, intelligent household appliances and the like.
The most common flyback topology structure of the current switching power supply has the advantages of simple structure, high reliability, wide voltage boosting and reducing range, electrical isolation for input and output, multiplexed output and the like. Secondary power supply development often uses this topology. But the driving capability of the power supply IC to the MOSFET transistor is limited in the current common design: most drive circuit is through a resistance direct drive MOS pipe of power IC series connection, and when the parasitic capacitance value of MOS pipe was too big, the energy that MOS pipe conduction needs was just bigger, and power IC drive peak current often is limited, leads to the driving force not enough, and pipe conduction speed is just slower, and rising edge high frequency oscillation probably appears, even reduce drive resistance, the driving force is not too big improvement.
Disclosure of Invention
The utility model provides a weak point in developing and using to secondary power supply provides a DC-DC flyback switching power supply converting circuit, and it can promote the driving force, accomplishes the charging process to MOS pipe grid input capacitance charge rapidly, has reduced turn-off time simultaneously, and the switching tube can fast switch and has avoided the high frequency oscillation of rising edge.
The flyback switching power supply based on control chip that this disclosure provides includes: the control chip used as a switch control circuit and the MOS tube switch circuit (5) used as a high-frequency switch, wherein a drive circuit (4) is arranged between the output end of the control chip and the input end of the MOS tube switch circuit, and the control chip comprises: n type and P type triode and first resistance, wherein:
the output end of the switch control circuit is connected with the base electrodes of the N-type triode and the P-type triode in parallel; the emitting electrode of the N-type triode is connected with the emitting electrode of the P-type triode and is connected with the first resistor; the other end of the first resistor is connected with a source electrode of the MOS tube; the collector electrode of the N-type triode is connected with a VCC auxiliary power supply; the collector of the P-type triode is connected with the internal ground.
Furthermore, a second resistor and a diode are connected in series between the source electrode of the MOS tube and the emitter electrode of the P-type triode and are used for rapidly discharging the capacitor voltage between the gate and the source of the MOS tube at the moment when the MOS tube is turned off.
Further, the diode is a schottky diode.
Further, the switching power supply further includes: starting circuit (1), flyback transformer (2), oscillating circuit (3), output rectifier filter circuit (7), steady voltage feedback circuit and VCC auxiliary power supply (10), wherein:
the DC power supply is externally input and is connected to the output end of the DC power supply through the starting circuit (1), the control chip, the driving circuit (4), the MOS tube switching circuit (5), the flyback transformer (2) and the output rectifying and filtering circuit (7) which are sequentially connected;
meanwhile, an externally input DC power supply is connected with a control chip through the flyback transformer (2) and the VCC auxiliary power supply (10) to provide a power supply for the control chip;
the output end of the output rectifying filter circuit (7) is input into the control chip through the voltage stabilizing feedback circuit (8, 9), and the oscillating circuit generates the sawtooth wave with fixed frequency and also inputs the sawtooth wave into the control chip.
Further, a control chip in the switching power supply adopts UC3845.
Compared with the prior art, the beneficial effect of this disclosure is: (1) by adding a driving circuit, the capability of driving the MOSEFET can be increased; (2) at the moment of MOS turn-off, the driving circuit provides a path with low impedance as much as possible for rapid discharge of capacitance voltage between the gate and the source of the MOSFET, thereby ensuring that the switching tube can be turned off rapidly; (3) the use of fast recovery diodes reduces turn-off time while reducing turn-off losses.
Drawings
The foregoing and other objects, features and advantages of the disclosure will be apparent from the following more particular descriptions of exemplary embodiments of the disclosure as illustrated in the accompanying drawings wherein like reference numbers generally represent like parts throughout the exemplary embodiments of the disclosure.
Fig. 1 is a schematic diagram of an overall structure of an exemplary embodiment of a flyback switching power supply according to the present disclosure;
FIG. 2 is a diagram of a driving circuit thereof;
fig. 3 is a detailed circuit layout diagram of a novel DC-DC flyback converter circuit according to the present disclosure;
fig. 4 is a diagram of an exemplary transformer structure.
Detailed Description
Preferred embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While the preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.
The present disclosure provides a flyback topology switching power supply based on a control chip, an exemplary embodiment of which is shown in fig. 1, and includes:
the circuit comprises a starting circuit (1), a transformer (2), a control circuit based on a control chip, a driving circuit (4), an MOS tube switching circuit (5), a current feedback circuit (6), an output rectifying filter circuit (7), voltage-stabilizing feedback circuits (8, 9), a VCC auxiliary circuit (10) and an RCD clamping circuit (11).
Wherein, the control chip selects UC3845, and the chip can be replaced according to the use condition.
In the figure, the driving circuit is further shown in fig. 2, most of the driving circuits directly drive the MOS transistor by serially connecting a resistor through the power IC, and the driving circuit may not work normally due to insufficient maximum driving peak current of the power IC, so that not only the conduction speed is relatively slow, but also high-frequency oscillation may occur on the rising edge, and even if the driving resistor is reduced, the improvement is not too great. Therefore, the N-type triode and the P-type triode are connected aiming at the insufficient driving capability, the driving circuit can improve the current capability and rapidly complete the charging process of the grid input capacitor charge; and the topology reduces the time required for conduction, the switching tube can be quickly switched on, and the high-frequency oscillation of the rising edge is avoided.
Meanwhile, in order to accelerate the turn-off of the MOS tube, a diode D4 and a resistor R11 are connected in parallel at a driving resistor R10, the design provides a path with low impedance as much as possible at the moment of the turn-off of the MOS tube for the rapid discharge of capacitance voltage between the grid and the source of the MOSFET tube, so that the switching tube can be ensured to be turned off rapidly, wherein the D4 uses a fast recovery diode, the turn-off time is reduced, the loss during turn-off is reduced, and the resistor R11 prevents overlarge current during turn-off and burns off a power supply IC.
The novel DC-DC flyback conversion circuit based on the driving circuit is shown in the attached figure 3, wherein:
1 starting a circuit part: after an input DC voltage passes through a filter capacitor, one section of the input DC voltage is connected with a starting resistor R0, and the other end of the starting resistor is connected with a power supply end of a control chip U1.
2, transformer: flyback transformer and VCC auxiliary circuit's transformer constitute, flyback transformer's source avris is connected with the drain end of input DC power end and MOSFET pipe Q1 respectively, flyback transformer's secondary avris comprises first output side and VCC auxiliary circuit side, the first order output of secondary avris and filter circuit input connection, VCC auxiliary circuit side be connected with diode D3 and electric capacity C4.
3, an oscillating circuit: the output frequency RT/CT end of the control chip U1 is adjusted to be connected with a fixed resistor and a capacitor in series, so that a sawtooth wave with fixed frequency is generated.
4, a driving circuit: the power supply circuit is composed of N-type and P-type triodes, diodes and resistors, wherein an output end OUT of a U1 of a control chip is connected with bases of the N-type and P-type triodes in series, an N-type collector and a P-type emitter are connected with R10 in series, the other side of R10 is connected with a grid electrode of an MOSFET (metal-oxide-semiconductor field effect transistor) tube Q1, in order to protect a driving circuit, a Schottky diode D4 and a resistor R11 are connected in parallel with the driving resistor R10, and when the MOSEFT tube Q1 is turned off, redundant electric energy flows into the inner ground of the control chip U1 through the Schottky diode D4 and the resistor R11, so that residual electric energy is released.
5mos tube switching circuit: the high-voltage power supply is composed of an MOSFET (metal oxide semiconductor field effect transistor) tube and a resistor, wherein the drain end of the MOSFET tube Q1 is connected with the source side outlet of a flyback transformer, and the source electrode of the MOSFET tube Q1 is connected with a current sampling resistor R11 and then connected to GND (ground potential).
6 current feedback circuit: the current sampling resistor R14 is composed of a resistor and a capacitor, one end of the current sampling resistor R14 is connected with the MOSFET and the R11, and the other end of the current sampling resistor R14 is connected with the ISENSE end of the control chip.
7, outputting a finishing filter circuit: the DC power supply comprises a diode D2, a resistor R2, capacitors C5, C6 and C7, wherein one end of the diode D2 is connected with a first-stage output end of the secondary side of the transformer, the other end of the diode D2 is connected with the ends of the capacitors C5 and C6 and then connected with a DC power supply output end, the capacitors C5 and C6 are connected in parallel and connected with an isolation ground DGND, and the R2 and the C7 are connected in series to form an RC filtering short circuit and connected in parallel at the diode D2, so that output ripples are reduced.
8.9 voltage regulation feedback circuit: the voltage stabilizing circuit is composed of sampling resistors R4 and R7 and a controllable precision voltage stabilizing source U2, wherein the sampling resistors R4 and R7 are connected in series, the resistor R4 is connected with a DC power output end, the resistor R7 is connected with a DGND (ground potential difference) which is isolated, a reference electrode of the controllable precision voltage stabilizing source U2 is connected between the resistor R4 and the resistor R7, the reference voltage at the reference electrode is designed to be 2.5V, RC filtering is formed by a resistor R6 and a capacitor C8, the resistor R6 is connected with a cathode at the end of the controllable precision voltage stabilizing source U2, and the capacitor C8 is connected with the reference electrode of the controllable precision voltage stabilizing source U2. High-speed opto-coupler source side feedback circuit then comprises resistance R3, R5, R8 and high-speed opto-coupler U3, resistance R3 is connected with DC power OUTPUT end, high-speed opto-coupler U3 OUTPUT OUTPUT and resistance R3 and controllable accurate steady voltage source negative pole end are connected, and high-speed opto-coupler U3's INPUT INPUT and resistance R8 are connected and are inserted ground GND, and the other end inserts the auxiliary circuit OUTPUT, and the voltage feedback end that inserts control chip U1 through resistance R9 between high-speed opto-coupler INPUT and the resistance R8 is connected.
11RCD clamp: the high-voltage power supply mainly comprises a resistor R1, a capacitor C3 and a diode D1, wherein one end of the resistor R1 is connected with the diode D1 after being connected with the capacitor C3 in parallel, the other end of the resistor R1 is connected with an input DC voltage end, and the diode D1 is connected with a source electrode of a MOSFET Q1.
A control chip: u1 adopts UC3845 chip, and the pin of this chip includes: the circuit comprises a compensation end, a voltage feedback end, a current sampling end, an output frequency adjusting end, a reference output end, a power supply end, an output end and a ground end. The power end is connected with the output of the flyback auxiliary circuit to provide power for the control chip, the compensation end series resistor R12 and the voltage feedback end series resistor R13 are connected with the capacitor C9 and then connected with the output end of the optical coupler in the voltage stabilization feedback end, the feedback signal is amplified by an error amplifier in the chip and is subjected to fusion modulation with the generated ground PWM triangular wave, and therefore the square wave with natural frequency is generated to drive the action of the MOSFET high-frequency switch Q1. The current sampling end series resistor R14 is connected with a source electrode sampling resistor of the MOSFET high-frequency switch Q1 and then connected to the ground, PWM waves can judge and conduct an output switch according to the signal, meanwhile, the pin is provided with a voltage mode control configuration device or added with harmonic compensation, the specific series resistor and the specific capacitor of an output frequency end are adjusted to be connected to the ground, the reference output end is connected to the ground after being connected with the capacitor in series, when the working frequency is fixed, the frequency is set through a voltage feedback end and the series resistor of the output frequency end, the ground end is a signal and power feedback ground, the output end is connected with a resistor in series to drive the MOSFET high-frequency switch Q1, and in order to prevent overshoot generated by high impedance of a power supply and the ground, a Schottky diode D4 and a resistor R11 are connected to the output drive resistor in parallel.
Wherein the transformer is shown in fig. 4, according to the design parameters of the transformer of the present disclosure, the use example is DC25V to DC 5V; is to be designedThe parameters were calculated as follows: output voltage is 22 VDC-27 VDC, conversion efficiency is 80%, switching frequency: 200kHz, output voltage: 5V, output current: 1A-5A, output ripple: 25mVp-p, duty cycle: 0.45 of; according to the set technical parameter indexes, the turn ratio of the transformer is obtained through calculation: 4, primary winding number: 8 turns, secondary turns: 2 turns, VCC auxiliary circuit winding number of turns: 4 turns, primary side inductance: 18uH, secondary inductance 1.5uH, VCC auxiliary circuit winding inductance: 4Uh; calculating according to AP method to obtain AP value of 0.1475cm 4 An EE22 type core made of PC40 material is selected, and the Ae value is 41mm2, and the le value is 39.4mm.
This embodiment can provide the power for control chip and high-speed opto-coupler simultaneously through setting up drive circuit, converts high DC voltage into the small-size switching power supply of DC5V to within reducing the output ripple to 20mV, its on-load ability can reach about 25W.
The foregoing is illustrative of the present invention and various modifications and changes in form or detail will readily occur to those skilled in the art based upon the teachings herein and the application of the principles and principles disclosed herein, which are to be regarded as illustrative rather than restrictive on the broad principles of the present invention.
Claims (5)
1. A flyback switching power supply based on a control chip comprises: control chip used as switch control circuit, and MOS tube switch circuit (5) used as high frequency switch, characterized in that, there is a drive circuit (4) between the output of the control chip and the input of the MOS tube switch circuit, including: n type and P type triode and first resistance, wherein:
the output end of the switch control circuit is connected with the bases of the N-type triode and the P-type triode in parallel; the emitting electrode of the N-type triode is connected with the emitting electrode of the P-type triode and is connected with the first resistor; the other end of the first resistor is connected with a source electrode of the MOS tube; the collector electrode of the N-type triode is connected with a VCC auxiliary power supply; the collector of the P-type triode is connected with the internal ground.
2. The switching power supply according to claim 1, wherein a second resistor and a diode are further connected in series between the source of the MOS transistor and the emitter of the P-type triode, for rapidly discharging the voltage of the capacitor between the gate and the source of the MOS transistor at the instant when the MOS transistor is turned off.
3. The switching power supply according to claim 2, wherein the diode is a schottky diode.
4. The switching power supply according to claim 3, further comprising: starting circuit (1), flyback transformer (2), oscillating circuit (3), output rectifier filter circuit (7), steady voltage feedback circuit and VCC auxiliary power supply (10), wherein:
the DC power supply is externally input and is connected to the output end of the DC power supply through the starting circuit (1), the control chip, the driving circuit (4), the MOS tube switching circuit (5), the flyback transformer (2) and the output rectifying and filtering circuit (7) which are sequentially connected;
meanwhile, an externally input DC power supply is connected with a control chip through the flyback transformer (2) and the VCC auxiliary power supply (10) to provide a power supply for the control chip;
the output end of the output rectifying filter circuit (7) is input into the control chip through the voltage stabilizing feedback circuits (8, 9), the oscillating circuit generates sawtooth waves with fixed frequency and inputs the sawtooth waves into the control chip.
5. The switching power supply according to any of claims 1-4, wherein said control chip employs UC3845.
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| CN202222759690.1U CN218783723U (en) | 2022-10-19 | 2022-10-19 | Flyback switching power supply based on control chip |
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| CN202222759690.1U CN218783723U (en) | 2022-10-19 | 2022-10-19 | Flyback switching power supply based on control chip |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116885953A (en) * | 2023-07-13 | 2023-10-13 | 广州冠廷机电设备有限公司 | High-voltage conversion circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116885953A (en) * | 2023-07-13 | 2023-10-13 | 广州冠廷机电设备有限公司 | High-voltage conversion circuit |
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