CN215772940U

CN215772940U - Switch power supply using double-winding transformer

Info

Publication number: CN215772940U
Application number: CN202122031875.6U
Authority: CN
Inventors: 王本欣
Original assignee: Hunan Furuikang Electronics Co ltd
Current assignee: Hunan Furuikang Electronics Co ltd
Priority date: 2021-08-26
Filing date: 2021-08-26
Publication date: 2022-02-08
Anticipated expiration: 2031-08-26

Abstract

The utility model discloses a switching power supply adopting a double-winding transformer, which comprises an alternating current input interface, a rectification filter module, a voltage conversion module, a follow current rectification filter module, a voltage feedback module and a PWM/PFM control and switching module which are sequentially connected in series; the voltage conversion module comprises a transformer T1, a primary winding of the transformer T1 is connected with the output end of the rectification filter module after being connected with the PWM/PFM control and switch module U1 in series, and a secondary winding of the transformer T1 is connected with the follow current rectification filter module; the PWM/PFM control and switch module controls the PWM/PFM of the power switch inside the PWM/PFM control module according to the change amount of the output voltage; according to the utility model, external auxiliary windings are not needed for power supply, so that the main transformer is simple in structure, and voltage transformation transmission can be completed only by two windings; meanwhile, a VCC high-voltage starting and rectifying circuit which is necessary for the original traditional circuit is not required to be added, energy loss caused by long-term work of the starting circuit is avoided, the conversion efficiency of the power supply circuit is greatly improved, and meanwhile, ultralow standby power consumption can be achieved.

Description

Switch power supply using double-winding transformer

Technical Field

The utility model relates to a switching power supply, in particular to a switching power supply adopting a double-winding transformer.

Background

At present, a switching power supply on the market generally adopts at least three mutually inductive windings for supporting normal work of a circuit, namely a primary input winding, a secondary output winding and a chip VCC feedback winding, wherein each winding is provided with a matched circuit to work in a closed loop mode, and the circuit is complex and generates power loss due to the essential work of the circuit.

Therefore, how to design a switching power supply with simple structure and low power is an urgent technical problem to be solved in the industry.

SUMMERY OF THE UTILITY MODEL

In order to solve the above-mentioned defects in the prior art, the present invention provides a switching power supply using a double-winding transformer.

The technical scheme adopted by the utility model is to design a switching power supply adopting a double-winding transformer, which comprises an alternating current input interface, a rectifying and filtering module, a voltage conversion module, a follow current rectifying and filtering module, a voltage feedback module and a PWM/PFM control and switching module which are sequentially connected in series; the rectification filtering module is connected with the alternating current and used for rectifying and filtering the alternating current and then outputting direct current; the voltage conversion module comprises a transformer T1, the transformer T1 adopts double windings, a primary winding of the transformer T1 is connected with the output end of the rectification filter module after being connected with the PWM/PFM control and switch module U1 in series, and a secondary winding of the transformer T1 is connected with the follow current rectification filter module; the follow current rectification filtering module rectifies and filters the pulse current output by the secondary winding and outputs the pulse current to a load; the voltage feedback module is used for feeding back the variation of the output voltage caused by the variation of the load; and the PWM/PFM control and switch module controls the power switch in the PWM/PFM control module according to the change amount of the output voltage.

The input end OC of the PWM/PFM control and switch module is connected with the primary winding of the transformer T1, the grounding end GND of the PWM/PFM control and switch module is grounded, and a fifth capacitor C5 is connected between the power end VDD and the ground; when the switching power supply is powered on, the input terminal OC charges the fifth capacitor C5 through the power supply terminal VDD, so that the power supply terminal VDD reaches the operating voltage.

And an EMI module is connected between the alternating current input interface and the rectifying and filtering module in series.

The freewheeling rectification filter module comprises a second diode D2, the anode of the second diode D2 is connected with the secondary winding of the transformer T1, the cathode of the second diode D2 outputs direct current, and the two ends of the second diode D2 are connected with a sixth resistor R6 and a seventh capacitor C7 in series.

And the output end of the follow current rectifying and filtering module is connected with the EMI module in series.

The voltage feedback module comprises a photoelectric coupling tube and a three-terminal voltage-regulator tube U3, a tenth resistor R10 and an eleventh resistor R11 are connected between the cathode of the second diode D2 and a virtual ground in series, the connection point of the tenth resistor R10 and the eleventh resistor R11 is connected with one end of a tenth capacitor C10 and a twelfth resistor and the control end of the three-terminal voltage-regulator tube U3, one end of the twelfth resistor and the anode of the three-terminal voltage-regulator tube U3 are connected with the virtual ground, the other end of the tenth capacitor C10 is connected with one end of a ninth resistor R9, the other end of the ninth resistor R9 is connected with the cathode of the three-terminal voltage-regulator tube U3, a seventh resistor R7 and an eighth resistor R8 are connected between the cathode of the second diode D2 and the cathode of the three-terminal voltage-regulator tube U3 in series, the two ends of the eighth resistor R8 are connected with the input end of the photoelectric coupling tube in parallel, the collector of the photoelectric coupling tube is connected with the power supply terminal of the PWM/PFM control and switch module, the emitter of the photoelectric coupling tube is connected with the feedback signal feedback module VDD and the fourth capacitor C4 of the PWM/FB control and the switch module, the other end of the fourth capacitor C4 is grounded, and an isolation capacitor CY1 is connected in series between the virtual ground and the ground.

The two ends of the primary winding of the transformer T1 are connected in parallel with a freewheeling module, the freewheeling module comprises a second resistor R2, a third resistor R3, a fourth resistor R4, a second capacitor C2 and a first diode D1, wherein one end of the second resistor C2, the second resistor R2 and the third resistor R3 is connected with the anode of the output end of the rectifying and filtering module and one end of the primary winding, the other end of the second capacitor C2, the second resistor R2 and the other end of the third resistor R3 are connected with one end of the fourth resistor R4, the other end of the fourth resistor R4 is connected with the cathode of the first diode D1, and the anode of the first diode D1 is connected with the other end of the primary winding and the input end OC of the PWM/PFM control and switch module.

The technical scheme provided by the utility model has the beneficial effects that:

according to the utility model, the purpose of self-power supply of the module is achieved through PWM/PFM control and intelligent start-stop control of a high-voltage start current source arranged in the switch module, the current consumption of the chip is provided, and external auxiliary windings are not needed; therefore, the main transformer has simple structure, and can complete voltage transformation transmission only by two windings; meanwhile, a VCC high-voltage starting and rectifying circuit which is necessary by the original traditional circuit is not required to be added, energy loss caused by long-term work of the starting circuit is avoided, power loss of the VCC rectifying circuit is avoided, the conversion efficiency of the power supply circuit is greatly improved, and meanwhile, ultralow standby power consumption can be achieved.

Drawings

The utility model is described in detail below with reference to examples and figures, in which:

FIG. 1 is a schematic block diagram of a preferred embodiment of the present invention;

FIG. 2 is a circuit diagram of the preferred embodiment of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the utility model and are not intended to limit the utility model.

The utility model discloses a switching power supply adopting a double-winding transformer, which refers to a schematic block diagram shown in figure 1 and comprises an alternating current input interface, a rectification filter module, a voltage conversion module, a follow current rectification filter module, a voltage feedback module and a PWM/PFM control and switching module which are sequentially connected in series; the rectification filtering module is connected with the alternating current and used for rectifying and filtering the alternating current and then outputting direct current; the voltage conversion module comprises a transformer T1, the transformer T1 adopts double windings, a primary winding of the transformer T1 is connected with the output end of the rectification filter module after being connected with the PWM/PFM control and switch module U1 in series, and a secondary winding of the transformer T1 is connected with the follow current rectification filter module; the follow current rectification filtering module rectifies and filters the pulse current output by the secondary winding and outputs the pulse current to a load; the voltage feedback module is used for feeding back the variation of the output voltage caused by the variation of the load; and the PWM/PFM control and switch module controls the power switch in the PWM/PFM control module according to the change amount of the output voltage.

The utility model provides self-powered current consumption of the chip through the PWM/PFM control and the switch module without providing electric energy by an external auxiliary winding. The design of the transformer is simplified, a VCC high-voltage starting circuit and a rectifying circuit are saved, the reactive loss is reduced, the conversion efficiency of a power circuit is improved, the ultra-low standby power consumption is realized, the energy-saving requirement is fully embodied, and the market competitiveness of the power supply is greatly improved.

Referring to the circuit diagram of the preferred embodiment shown in fig. 2, the input terminal OC of the PWM/PFM control and switch module U1 is connected to the primary winding of the transformer T1, the ground terminal GND thereof is connected to ground, and a fifth capacitor C5 is connected between the power terminal VDD thereof and ground; when the switching power supply is powered on, the input terminal OC charges the fifth capacitor C5 through the power supply terminal VDD, so that the power supply terminal VDD reaches the operating voltage. When the switching power supply enters normal operation, power is continuously supplied to VDD from the inside of U1.

In order to achieve a good filtering effect, an EMI module is connected in series between the AC input interface and the rectifying and filtering module. In the circuit diagram of the preferred embodiment shown in fig. 2, CX1, R1A, R1B, R1C, R1D, and LF1 constitute an EMI module.

Referring to the circuit diagram of the preferred embodiment shown in fig. 2, the freewheeling rectification filter module includes a second diode D2, an anode of the second diode D2 is connected to the secondary winding of the transformer T1, a cathode of the second diode D2 outputs direct current, and a sixth resistor R6 and a seventh capacitor C7 are connected in series to both ends of the second diode D2. The sixth resistor R6 and the seventh capacitor C7 serve as a absorption loop of the second diode D2 to absorb the directional spike of D2.

In order to filter the output current, the output end of the follow current rectification filter module is connected with the EMI module in series. In the preferred embodiment circuit diagram shown in fig. 2, C9, R13, LF2 constitute an EMI module.

Referring to the circuit diagram of the preferred embodiment shown in fig. 2, the voltage feedback module includes a photocoupler tube and a three-terminal regulator tube U3, a tenth resistor R10 and an eleventh resistor R11 are connected in series between the cathode of the second diode D2 and the virtual ground, a connection point of the tenth resistor R10 and the eleventh resistor R11 is connected to one end of a tenth capacitor C10 and a twelfth resistor and the control end of the three-terminal regulator tube U3, one end of the twelfth resistor and the anode of the three-terminal regulator tube U3 are connected to the virtual ground, the other end of the tenth capacitor C10 is connected to one end of a ninth resistor R9, the other end of the ninth resistor R9 is connected to the cathode of the three-terminal regulator tube U3, a seventh resistor R7 and an eighth resistor R8 are connected in series between the cathode of the second diode D2 and the cathode of the three-terminal regulator tube U3, two ends of the eighth resistor R8 are connected in parallel to the input end of the photocoupler tube, the collector of the photocoupler tube is connected to the VDD of the PWM photocoupler/PFM control and switching module, the emitter of the photoelectric coupling tube is connected with the signal feedback end FB of the PWM/PFM control and switch module and one end of a fourth capacitor C4, the other end of the fourth capacitor C4 is grounded, and an isolation capacitor CY1 is connected between the virtual ground and the ground in series.

And two ends of the primary winding of the transformer T1 are connected with a follow current module in parallel, and when the PWM/PFM control and switch module is switched off, the current in the primary winding continues current from the module. Referring to the circuit diagram of the preferred embodiment shown in fig. 2, the freewheel module includes a second resistor R2, a third resistor R3, a fourth resistor R4, a second capacitor C2 and a first diode D1, wherein one end of the second capacitor C2, the second resistor R2 and the third resistor R3 is connected to the positive electrode of the output terminal of the rectifying and filtering module and one end of the primary winding, the other end of the second capacitor C2, the second resistor R2 and the third resistor R3 is connected to one end of the fourth resistor R4, the other end of the fourth resistor R4 is connected to the cathode of the first diode D1, and the anode of the first diode D1 is connected to the other end of the primary winding and the input terminal OC of the PWM/PFM control and switch module.

It should be noted that, in the preferred embodiment (see fig. 2), the fuse F1 and the thermistor NTC1 are connected in series with the live line of the ac input interface, and the varistor MOV1 is connected between the live line and the neutral line. Short circuit, overcurrent and overvoltage protection are respectively realized.

The working principle of the utility model is described in detail below with reference to fig. 2: the utility model provides a control scheme of a secondary feedback type full-voltage input flyback AC-DC high-performance quasi-resonant switching power supply which accords with a 6-level energy efficiency standard. The scheme integrates a high-voltage switch power tube and adopts a CMOS circuit design with high integration level; the circuit also comprises quasi-resonance detection, SLEEP ultra-low standby, integration of a high-voltage constant-current starting circuit and a self-power supply technology, no need of an external starting resistor, few peripheral elements, simple transformer design (the transformer for isolating the output circuit only needs two windings including a primary winding and a secondary winding), and the like. A PWM quasi-resonant circuit is arranged in the power supply, so that the power supply conversion efficiency is increased, and good EMC characteristics are ensured.

The PWM/PFM control and switch module is internally provided with a high-voltage starting current source; when the voltage of U1 VCC is smaller than the starting voltage of U1 during power-on starting, starting 1mA current charges the energy storage capacitor (fifth capacitor C5) outside the power supply terminal VDD through the internal starting circuit of the input terminal OC. When the VDD voltage reaches the 10V start voltage, the start-up process ends with the start-up current source turned off, and the control logic begins outputting PWM pulses. After the power-on starting is finished, in order to prevent the transformer magnetic core saturation possibly generated in the output voltage establishing process and the overlarge stress of the power tube and the secondary rectifier tube, a soft starting circuit is arranged in a chip, and the maximum primary peak current is 0.5 x Ip in the soft starting time. The operating frequency gradually increases from 20Khz to 65Khz as the output voltage and power increase. One PWM cycle consists of three parts: the inductance charges (the switch tube is opened) stage, inductance discharge stage (the switch tube is closed), OC resonance stage, and the chip adopts accurate resonance output mode, when detecting OC resonance to minimum voltage, opens PWM output, opens the switch tube and charges for the inductance, has reduced the switching loss of switch tube like this, has improved the conversion efficiency of power. In order to realize the standby with ultra-low power consumption, when the chip is designed with a SLEEP mode and the output power gradually drops to be close to the standby state, the PWM/PFM control and switch module enters the SLEEP mode. When the SLEEP mode is in standby, the chip quiescent current is only 25uA, and the ultralow standby power consumption (below 30 mW) of the system can be realized.

The foregoing examples are illustrative only and are not intended to be limiting. Any equivalent modifications or variations without departing from the spirit and scope of the present application should be included in the claims of the present application.

Claims

1. A switching power supply using a double-winding transformer is characterized in that: the device comprises an alternating current input interface, a rectification filter module, a voltage conversion module, a follow current rectification filter module, a voltage feedback module and a PWM/PFM control and switch module which are sequentially connected in series; wherein

The rectification filtering module is connected with the alternating current and used for rectifying and filtering the alternating current and then outputting direct current;

the voltage conversion module comprises a transformer T1, the transformer T1 adopts double windings, a primary winding of the transformer T1 is connected with the output end of the rectification filter module after being connected with the PWM/PFM control and switch module U1 in series, and a secondary winding of the transformer T1 is connected with the follow current rectification filter module;

the follow current rectification filtering module rectifies and filters the pulse current output by the secondary winding and outputs the pulse current to a load;

the voltage feedback module is used for feeding back the variation of the output voltage caused by the variation of the load;

and the PWM/PFM control and switch module controls the power switch in the PWM/PFM control module according to the change amount of the output voltage.

2. The switching power supply using the double-winding transformer as claimed in claim 1, wherein: the input end OC of the PWM/PFM control and switch module is connected with the primary winding of the transformer T1, the grounding end GND of the PWM/PFM control and switch module is grounded, and a fifth capacitor C5 is connected between the power end VDD and the ground; when the switching power supply is powered on, the input terminal OC charges the fifth capacitor C5 through the power supply terminal VDD, so that the power supply terminal VDD reaches the operating voltage.

3. The switching power supply using the double-winding transformer as claimed in claim 1, wherein: and an EMI module is connected between the alternating current input interface and the rectifying and filtering module in series.

4. The switching power supply using the double-winding transformer as claimed in claim 2, wherein: the freewheeling rectification filter module comprises a second diode D2, the anode of the second diode D2 is connected with the secondary winding of the transformer T1, the cathode of the second diode D2 outputs direct current, and the two ends of the second diode D2 are connected with a sixth resistor R6 and a seventh capacitor C7 in series.

5. The switching power supply using the double-winding transformer as claimed in claim 1, wherein: and the output end of the follow current rectifying and filtering module is connected with the EMI module in series.

6. The switching power supply using the double-winding transformer as claimed in claim 4, wherein: the voltage feedback module comprises a photoelectric coupling tube and a three-terminal voltage-regulator tube U3, a tenth resistor R10 and an eleventh resistor R11 are connected between the cathode of the second diode D2 and a virtual ground in series, the connection point of the tenth resistor R10 and the eleventh resistor R11 is connected with one end of a tenth capacitor C10 and a twelfth resistor and the control end of the three-terminal voltage-regulator tube U3, one end of the twelfth resistor and the anode of the three-terminal voltage-regulator tube U3 are connected with the virtual ground, the other end of the tenth capacitor C10 is connected with one end of a ninth resistor R9, the other end of the ninth resistor R9 is connected with the cathode of the three-terminal voltage-regulator tube U3, a seventh resistor R7 and an eighth resistor R8 are connected between the cathode of the second diode D2 and the cathode of the three-terminal voltage-regulator tube U3 in series, the two ends of the eighth resistor R8 are connected with the input end of the photoelectric coupling tube in parallel, the collector of the photoelectric coupling tube is connected with the power supply terminal of the PWM/PFM control and switch module, the emitter of the photoelectric coupling tube is connected with the feedback signal feedback module VDD and the fourth capacitor C4 of the PWM/FB control and the switch module, the other end of the fourth capacitor C4 is grounded, and an isolation capacitor CY1 is connected in series between the virtual ground and the ground.

7. The switching power supply using the double-winding transformer as claimed in claim 2, wherein: the two ends of the primary winding of the transformer T1 are connected in parallel with a freewheeling module, the freewheeling module comprises a second resistor R2, a third resistor R3, a fourth resistor R4, a second capacitor C2 and a first diode D1, wherein one end of the second resistor C2, the second resistor R2 and the third resistor R3 is connected with the anode of the output end of the rectifying and filtering module and one end of the primary winding, the other end of the second capacitor C2, the second resistor R2 and the other end of the third resistor R3 are connected with one end of the fourth resistor R4, the other end of the fourth resistor R4 is connected with the cathode of the first diode D1, and the anode of the first diode D1 is connected with the other end of the primary winding and the input end OC of the PWM/PFM control and switch module.