CN210297549U - Switching power supply based on flyback transformer - Google Patents
Switching power supply based on flyback transformer Download PDFInfo
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- CN210297549U CN210297549U CN201921310318.4U CN201921310318U CN210297549U CN 210297549 U CN210297549 U CN 210297549U CN 201921310318 U CN201921310318 U CN 201921310318U CN 210297549 U CN210297549 U CN 210297549U
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Abstract
The utility model provides a switching power supply based on flyback transformer belongs to power technical field. The problem that output voltage is unstable due to delay in the switching power supply in the prior art is solved. The switch power supply comprises a primary circuit, a transformer, a secondary circuit, a voltage sampling module, an amplifier, a comparator, a PWM signal generating circuit and a duty ratio detection circuit, wherein the voltage sampling module is connected to a secondary output loop to sample output voltage and convey the output voltage to the negative input end of the amplifier, the output end of the amplifier is connected with the positive input end of the comparator, the output end of the comparator is connected with the input end of the PWM signal generating circuit, the output end of the PWM signal generating circuit is connected with the switch end of the primary circuit, the input end of the duty ratio detection circuit is connected with the output end of the PWM signal generating circuit, and the output end of the duty ratio detection circuit is connected with the negative input end of. The switching power supply solves the problem of time delay of sampling on the inductor and has high working frequency.
Description
Technical Field
The utility model belongs to the technical field of switching power supply, in particular to switching power supply based on flyback transformer.
Background
The switching power supply adopts a power semiconductor device as a switching device, controls the duty ratio of the switching device to adjust the output voltage through periodic discontinuous work, has the advantages of simple structure, small volume, low cost, no filter inductance, capability of realizing isolated output and the like, and is widely applied to low-power direct current application occasions, such as a charger, a set top box, an auxiliary power supply of a large power supply and the like. Under the above working conditions, it is necessary to provide a stable output voltage or current and to make the voltage regulation rate or the load regulation rate of the circuit meet the design criteria, so that it is necessary to perform closed-loop control on the circuit to resist the influence of external disturbances such as input voltage disturbance and load disturbance on the output. For the above reasons, the conventional current mode switching power supply performs PWM (pulse Width Modulation) processing and filtering processing on an input dc voltage signal, performs error amplification on the filtered dc voltage signal, and sends the amplified dc voltage signal to a comparator, the comparator compares the error-amplified signal with a current signal sampled from an inductor of a low-pass filter, generates a PWM signal with a certain duty ratio based on a level signal generated after the comparison, and drives a switching element such as a thyristor and the like using the PWM signal, thereby obtaining a stable output voltage signal.
In the existing switching power supply, due to the pressure of product space and cost and miniaturization of external devices, the switching frequency of the switching power supply is required to be higher and higher, but in the current mode switching power supply, a comparator in a control loop needs to collect current on an inductor through a sampling circuit, but the current sampling circuit has the limitation of time delay and cannot accurately work under higher frequency.
Disclosure of Invention
In view of this, the embodiment of the present invention provides a flyback transformer-based switching power supply that can be stable at higher frequencies.
The purpose of the utility model can be realized by the following technical proposal: a switching power supply based on a flyback transformer comprises a primary side circuit, a transformer, a secondary side circuit and a feedback control circuit, and is characterized in that the secondary side circuit comprises a main output loop and a secondary output loop, the main output loop and the secondary output loop are both connected with an output rectifying filter circuit, the feedback control circuit comprises a voltage sampling module, an amplifier, a comparator, a PWM signal generating circuit and a duty ratio detection circuit, the voltage sampling module is connected with the secondary output loop to sample output voltage and transmit the output voltage to the negative input end of the amplifier, the positive input end of the amplifier is used for inputting reference voltage, the output end of the amplifier is connected with the positive input end of the comparator, the output end of the comparator is connected with the input end of the PWM signal generating circuit, and the output end of the PWM signal generating circuit is connected with the switching end of the primary side circuit, the input end of the duty ratio detection circuit is connected to the output end of the PWM signal generation circuit, and the output end of the duty ratio detection circuit is connected to the negative input end of the comparator.
In the switching power supply based on the flyback transformer, the primary side circuit comprises an alternating current input module, an input rectification filter module and an MOS transistor Q1, the input rectification filter circuit comprises a rectifier bridge formed by a diode D1, a diode D2, a diode D3 and a diode D4, a capacitor C1, a capacitor C2, a resistor R0 and a common-mode inductor L1, the input end of the input rectification filter circuit is connected with the alternating current input module, the positive output end of the input rectification filter circuit is connected with the positive electrode of the primary side winding of the transformer, and the negative output end of the input rectification filter circuit is connected with the source electrode of the MOS transistor Q1; the drain electrode of the MOS tube Q1 is connected with the negative electrode of the primary winding of the transformer; and the grid electrode of the MOS tube Q1 is used as the switching end of the primary side circuit and is connected with the output end of the PWM signal generating circuit.
In the switching power supply based on the flyback transformer, the primary side circuit further comprises an RDC buffer circuit, the RDC buffer circuit comprises a capacitor C3, a resistor R1 and a diode D5, a drain of the MOS transistor Q1 is respectively connected with one end of the capacitor C3, one end of the resistor R1 and a cathode of the diode D5, the other end of the capacitor C3 and the other end of the resistor R1 are both connected with a positive output end of the input rectification filter circuit, and an anode of the diode D5 is connected with a cathode of the primary side winding of the transformer. The RDC buffer circuit is used for controlling surge current and overshoot voltage at the moment of power supply insertion, and plays a role in absorption protection.
In the switching power supply based on the flyback transformer, the voltage sampling module includes a resistor R3 and a resistor R4, one end of the resistor R3 is connected to the positive output end of the secondary output loop, the other end of the resistor R3 is grounded through the resistor R4, and the other end of the resistor R3 is connected to the negative input end of the amplifier.
In the switching power supply based on the flyback transformer, the duty ratio detection circuit comprises a resistor R5 and a capacitor C6, one end of the resistor R5 is connected to the output end of the PWM signal generation circuit, the other end of the resistor R5 is grounded through the capacitor C6, and the other end of the resistor R5 is connected to the negative input end of the comparator.
In the switching power supply based on the flyback transformer, the PWM generating circuit includes an RS flip-flop and a clock circuit, a reset terminal of the RS flip-flop is connected to an output terminal of the clock circuit, a set terminal of the RS flip-flop is connected to an output terminal of the comparator, and an output terminal of the RS flip-flop is connected to a switching terminal of the primary circuit.
Compared with the prior art, this switching power supply based on flyback transformer has following advantage: by adopting the flyback transformer, a secondary inductor is not needed on a secondary side circuit, and a complex acquisition circuit is avoided to acquire signals from the inductor, so that the complexity of the switching power supply is reduced, the problem of time delay in the feedback signal acquisition process is solved, and the working frequency is improved.
Drawings
Fig. 1 is a schematic circuit diagram of an embodiment of the present invention.
Detailed Description
The following are specific embodiments of the present invention and the accompanying drawings are used to further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.
As shown in fig. 1, the switching power supply based on the flyback transformer includes a primary side circuit, a transformer, a secondary side circuit and a feedback control circuit, the secondary side circuit includes a primary output circuit and a secondary output circuit, both the primary output circuit and the secondary output circuit are connected with an output rectifying filter circuit, the feedback control circuit includes a voltage sampling module, an amplifier, a comparator, a PWM signal generating circuit and a duty ratio detecting circuit, the voltage sampling module is connected to the secondary output circuit to sample the output voltage and transmit the output voltage to the negative input terminal of the amplifier, the positive input terminal of the amplifier is used for inputting a reference voltage, the output terminal of the amplifier is connected to the positive input terminal of the comparator, the output terminal of the comparator is connected to the input terminal of the PWM signal generating circuit, the output terminal of the PWM signal generating circuit is connected to the switch terminal of the primary side circuit, the input terminal of the duty ratio detecting circuit is connected to the, the output end of the duty ratio detection circuit is connected with the negative input end of the comparator.
Specifically, the primary side circuit comprises an alternating current input module, an input rectifying and filtering module, a MOS (metal oxide semiconductor) tube Q1 and an RDC (remote data center) buffer circuit. The input rectifying and filtering circuit comprises a rectifying bridge, a capacitor C1, a capacitor C2, a resistor R0 and a common-mode inductor L1; the rectifier bridge is composed of a diode D1, a diode D2, a diode D3 and a diode D4; the RDC snubber circuit includes a capacitor C3, a resistor R1, and a diode D5. The negative output end of the rectifier bridge is connected with the source electrode of the MOS transistor Q1; the drain electrode of the MOS transistor Q1 is respectively connected with one end of a capacitor C3, one end of a resistor R1 and the negative electrode of a diode D5; the drain electrode of the MOS tube Q1 is connected with the negative electrode of the primary winding of the transformer; the grid electrode of the MOS tube Q1 is used as the switching end of the primary side circuit and is connected with the output end of the PWM signal generating circuit. The input end of the rectifier bridge is connected with the alternating current input module, the positive output end of the rectifier bridge is connected with one end of a common mode inductor L1, the other end of the common mode inductor L1 is connected with the positive electrode of the primary winding of the transformer, the other end of a capacitor C3 and the other end of a resistor R1 respectively, the capacitor C1 and the capacitor C2 are connected between the positive output end and the negative output end of the rectifier bridge respectively, and the resistor R0 is connected at two ends of the common mode inductor L1 in parallel. The other end of the capacitor C3 and the other end of the resistor R1 are both connected with the other end of the common-mode inductor L1, and the anode of the diode D5 is connected with the cathode of the primary winding of the transformer.
The voltage sampling module is configured to sample the dc output voltage signal Vom to obtain a sampled voltage signal, and the coupling manner of the voltage sampling module and the auxiliary output circuit may be direct coupling, indirect coupling, or photoelectric coupling, which is not limited in this embodiment. The voltage sampling module comprises a resistor R3 and a resistor R4, one end of the resistor R3 is connected with the positive output end of the auxiliary output loop, the other end of the resistor R3 is grounded through a resistor R4, and the other end of the resistor R3 is connected with the negative input end of the amplifier.
The duty ratio detection circuit comprises a resistor R5 and a capacitor C6, one end of the resistor R5 is connected with the output end of the PWM signal generation circuit, the other end of the resistor R5 is grounded through the capacitor C6, and the other end of the resistor R5 is connected with the negative input end of the comparator. The duty ratio detection circuit collects the square wave type PWM signal directly output by the PWM signal generation circuit and converts the square wave type PWM signal into a triangular wave signal which is input to the negative input end of the comparator, so that the voltage signal of the negative input end of the comparator is directly converted from the square wave signal output by the PWM signal generation circuit, the complex collection circuit is avoided from collecting current from an inductor, the complexity of the switching power supply is reduced, the collection time is shortened, and the working frequency is improved.
The PWM generating circuit comprises an RS trigger and a clock circuit (represented by CLK in the figure), wherein the reset end of the RS trigger is connected with the output end of the clock circuit, the set end of the RS trigger is connected with the output end of the comparator, and the output end of the RS trigger is connected with the switching end of the primary side circuit. The clock circuit CLK is used for generating a periodic clock signal and outputting the clock signal to the reset terminal of the RS flip-flop.
The principle of the utility model is as follows:
the primary circuit converts a direct current input voltage signal rectified and filtered by the input rectifying and filtering circuit into a pulse output voltage signal according to a PWM signal input by a switch end of the primary circuit; the output rectifying and filtering circuit is used for filtering the pulse output voltage signal output by the main output loop or the auxiliary output loop to obtain a direct current output voltage signal, and the direct current output voltage signal is output at the output end of the switching power supply; the feedback control circuit samples the direct-current output voltage signal of the auxiliary output loop to obtain a sampling voltage signal, and inputs the sampling voltage signal to the negative input end of the amplifier; the positive input end of the amplifier inputs a reference voltage which is artificially set or generated by a reference voltage generating circuit; the output end of the amplifier is connected with the positive input end of the comparator, the PWM signal generating circuit generates a PWM signal according to the level signal output by the comparator and inputs the PWM signal to the MOS tube, and the duty ratio detection circuit converts the PWM signal into a triangular wave signal and inputs the triangular wave signal to the negative input end of the comparator. The switching circuit is designed based on the flyback transformer, and a secondary inductor is eliminated, so that a complex acquisition circuit is avoided from acquiring signals from the inductor, the complexity of the switching power supply is reduced, the sampling delay of a sampling resistor is reduced, and the working frequency is improved.
The specific embodiments described herein are merely illustrative of the spirit of the invention. Various modifications, additions and substitutions for the specific embodiments described herein may be made by those skilled in the art without departing from the spirit of the invention or exceeding the scope of the invention as defined in the accompanying claims.
Claims (6)
1. A switching power supply based on a flyback transformer comprises a primary side circuit, a transformer, a secondary side circuit and a feedback control circuit, and is characterized in that the secondary side circuit comprises a main output loop and a secondary output loop, the main output loop and the secondary output loop are both connected with an output rectifying filter circuit, the feedback control circuit comprises a voltage sampling module, an amplifier, a comparator, a PWM signal generating circuit and a duty ratio detection circuit, the voltage sampling module is connected with the secondary output loop to sample output voltage and transmit the output voltage to the negative input end of the amplifier, the positive input end of the amplifier is used for inputting reference voltage, the output end of the amplifier is connected with the positive input end of the comparator, the output end of the comparator is connected with the input end of the PWM signal generating circuit, and the output end of the PWM signal generating circuit is connected with the switching end of the primary side circuit, the input end of the duty ratio detection circuit is connected to the output end of the PWM signal generation circuit, and the output end of the duty ratio detection circuit is connected to the negative input end of the comparator.
2. The flyback transformer-based switching power supply of claim 1, wherein the primary circuit comprises an ac input module, an input rectifying filter module, and a MOS transistor Q1, the input rectifying filter circuit comprises a rectifier bridge formed by a diode D1, a diode D2, a diode D3, and a diode D4, a capacitor C1, a capacitor C2, a resistor R0, and a common-mode inductor L1, an input of the input rectifying filter circuit is connected to the ac input module, a positive output of the input rectifying filter circuit is connected to an anode of the primary winding of the transformer, and a negative output of the input rectifying filter circuit is connected to a source of the MOS transistor Q1; the drain electrode of the MOS tube Q1 is connected with the negative electrode of the primary winding of the transformer; and the grid electrode of the MOS tube Q1 is used as the switching end of the primary side circuit and is connected with the output end of the PWM signal generating circuit.
3. The flyback transformer-based switching power supply of claim 2, wherein the primary circuit further comprises an RDC snubber circuit, the RDC snubber circuit comprises a capacitor C3, a resistor R1 and a diode D5, the drain of the MOS transistor Q1 is connected to one end of the capacitor C3, one end of the resistor R1 and the cathode of the diode D5, respectively, the other end of the capacitor C3 and the other end of the resistor R1 are both connected to the positive output end of the input rectifying and filtering circuit, and the anode of the diode D5 is connected to the cathode of the primary winding of the transformer.
4. The flyback transformer-based switching power supply according to claim 1, 2 or 3, wherein the voltage sampling module comprises a resistor R3 and a resistor R4, one end of the resistor R3 is connected to the positive output end of the secondary output loop, the other end of the resistor R3 is connected to the ground through the resistor R4, and the other end of the resistor R3 is connected to the negative input end of the amplifier.
5. The flyback transformer-based switching power supply according to claim 1, 2 or 3, wherein the duty cycle detection circuit comprises a resistor R5 and a capacitor C6, one end of the resistor R5 is connected to the output terminal of the PWM signal generation circuit, the other end of the resistor R5 is connected to the ground through a capacitor C6, and the other end of the resistor R5 is connected to the negative input terminal of the comparator.
6. The flyback transformer-based switching power supply according to any one of claims 1, 2 or 3, wherein the PWM signal generating circuit comprises an RS flip-flop and a clock circuit, a reset terminal of the RS flip-flop is connected to an output terminal of the clock circuit, a set terminal of the RS flip-flop is connected to an output terminal of the comparator, and an output terminal of the RS flip-flop is connected to a switching terminal of the primary side circuit.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201921310318.4U CN210297549U (en) | 2019-08-13 | 2019-08-13 | Switching power supply based on flyback transformer |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201921310318.4U CN210297549U (en) | 2019-08-13 | 2019-08-13 | Switching power supply based on flyback transformer |
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| CN210297549U true CN210297549U (en) | 2020-04-10 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114290905A (en) * | 2021-12-31 | 2022-04-08 | 银川威力传动技术股份有限公司 | Active discharge circuit of motor controller |
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2019
- 2019-08-13 CN CN201921310318.4U patent/CN210297549U/en active Active
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114290905A (en) * | 2021-12-31 | 2022-04-08 | 银川威力传动技术股份有限公司 | Active discharge circuit of motor controller |
| CN114290905B (en) * | 2021-12-31 | 2024-05-24 | 银川威力传动技术股份有限公司 | Active discharging circuit of motor controller |
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