CN216146251U

CN216146251U - Flyback switching power supply and control device thereof

Info

Publication number: CN216146251U
Application number: CN202122239288.6U
Authority: CN
Inventors: 张岩; 雷龙; 翟志伟; 殷童欢; 霍星星; 魏兵戌
Original assignee: Gree Electric Appliances Inc of Zhuhai
Current assignee: Gree Electric Appliances Inc of Zhuhai
Priority date: 2021-09-14
Filing date: 2021-09-14
Publication date: 2022-03-29
Anticipated expiration: 2031-09-14

Abstract

The utility model discloses a control device of a flyback switching power supply and the flyback switching power supply, the device comprises: a PFC inductor as a primary winding of the transformer; the sampling unit is configured to sample a primary PFC current of the transformer and sample a secondary output voltage of the transformer; and the control unit is configured to control a driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, so that the direct current provided by the direct current power supply is converted into alternating current by controlling the switching tube to be switched on and switched off, and the alternating current is transmitted to the secondary winding of the transformer through the primary winding of the transformer. According to the scheme, the PFC inductor of the flyback switching power supply is used as the primary winding of the high-frequency transformer, so that the structure of the flyback switching power supply can be effectively simplified.

Description

Flyback switching power supply and control device thereof

Technical Field

The utility model belongs to the technical field of power supplies, particularly relates to a control device of a flyback switching power supply and the flyback switching power supply, and particularly relates to a novel control device of a household appliance power supply topology and the flyback switching power supply.

Background

In a related scheme, a household appliance power supply adopts a switching power supply, the topology of the switching power supply is a flyback power supply (namely, a flyback switching power supply), and the load capacity is generally dozens of watts. The flyback switching power supply has the structure that: after power factor correction, the bus gets electricity, and then the low-voltage multi-path output is realized through a flyback topology of a power supply IC (namely a power supply chip) and a high-frequency transformer, but the structure of the flyback switching power supply is complex.

The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.

SUMMERY OF THE UTILITY MODEL

The utility model aims to provide a control device of a flyback switching power supply and the flyback switching power supply, so as to solve the problems that the flyback switching power supply obtains electricity through a bus after power factor correction and then realizes low-voltage multi-path output through a flyback topology of a power supply IC and a high-frequency transformer, the structure of the flyback switching power supply is complex, and the effect that the structure of the flyback switching power supply can be effectively simplified by taking a PFC inductor of the flyback switching power supply as a primary winding of the high-frequency transformer is achieved.

The utility model provides a control device of a flyback switching power supply, which comprises: a PFC circuit and a transformer; the PFC circuit includes: a PFC inductor and a switching tube; the PFC inductor is used as a primary winding of the transformer; the control device of the flyback switching power supply comprises: a sampling unit and a control unit; the sampling unit is configured to sample a primary PFC current of the transformer and sample a secondary output voltage of the transformer; the control unit is configured to control a driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, so that direct current provided by a direct current power supply is converted into alternating current by controlling the switching tube to be switched on and switched off, and the alternating current is transmitted to a secondary winding of the transformer through a primary winding of the transformer.

In some embodiments, the PFC circuit further comprises: a diode module and a capacitor module; the synonym end of the primary winding of the transformer is connected to the anode of the diode module and also connected to the first connecting end of the switching tube; the second connecting end of the switch tube is connected to the cathode of the diode module after passing through the capacitor module; and the control end of the switching tube is used for receiving the driving signal.

In some embodiments, the number of secondary windings of the transformer is more than one; in more than one secondary winding of the transformer, the output end of each secondary winding supplies power to a load after passing through the corresponding rectifying module and the corresponding filtering module.

In some embodiments, in more than one secondary winding of the transformer, the synonym terminal of each secondary winding is connected to the anode of the corresponding rectification module; and the dotted end of each secondary winding is connected to the cathode of the corresponding rectifying module after passing through the capacitor module.

In some embodiments, the sampling unit includes: a first sampling unit and a second sampling unit; the sampling unit is used for sampling the primary PFC current of the transformer and sampling the secondary output voltage of the transformer, and comprises: the first sampling unit is configured to sample the working current of the switching tube to serve as the primary PFC current of the transformer, and the primary PFC current of the transformer is output in the form of voltage; the second sampling unit is configured to sample a voltage of a same-name end of a secondary winding of the transformer as a secondary output voltage of the transformer.

In some embodiments, the control unit comprises: the device comprises a first comparator, a PI controller, a second comparator and a driving circuit; the control unit controls the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, and comprises: the first comparator is configured to compare a reference voltage with a secondary side output voltage of the transformer to obtain a first voltage; the PI controller is configured to perform PI processing on the first voltage to obtain a second voltage; the controller is configured to compare the second voltage with a primary PFC current of the transformer to obtain a third voltage; the second comparator is configured to compare the third voltage with a secondary side output voltage of the transformer to obtain a driving voltage; the driving circuit is configured to generate a control signal as a driving signal for controlling the switching tube based on the driving voltage.

In some embodiments, further comprising: the control unit is further configured to determine whether the on-time or off-time of a switching tube in the PFC circuit reaches a given time, and if so, control a driving signal of the switching tube according to a primary PFC current of the transformer and a secondary output voltage of the transformer; otherwise, the secondary side output voltage of the transformer is increased according to a set increasing mode, and then the driving signal of the switching tube is controlled according to the primary side PFC current of the transformer and the secondary side output voltage of the transformer.

In another aspect, the present invention provides a flyback switching power supply, including: the control device of the flyback switching power supply is described above.

Therefore, according to the scheme of the utility model, the PFC inductor of the flyback switching power supply is used as the primary winding of the high-frequency transformer, the switching tube Q of the PFC circuit has the same function as the switching tube in the flyback switching power supply, and the primary PFC current I of the transformer is used_PFCAnd secondary output voltage Uo of the transformer, control the driving signal of the switch tube Q, and control the on or off of the switch tube QTurning off, converting the direct current into alternating current, and transmitting the energy to the secondary side of a high-frequency transformer T1 through the primary side of the high-frequency transformer T1; therefore, the PFC inductor of the flyback switching power supply is used as the primary winding of the high-frequency transformer, so that the structure of the flyback switching power supply can be effectively simplified.

Additional features and advantages of the utility model will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the utility model.

The technical solution of the present invention is further described in detail by the accompanying drawings and embodiments.

Drawings

Fig. 1 is a schematic structural diagram of a control device of a flyback switching power supply according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a power supply topology;

FIG. 3 is a schematic diagram of a novel power supply topology;

FIG. 4 is a schematic control flow diagram of a novel power supply topology;

fig. 5 is a flowchart illustrating a control method of the flyback switching power supply according to an embodiment of the present invention;

fig. 6 is a schematic flow chart of an embodiment of controlling the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer in the method of the present invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the specific embodiments of the present invention and the accompanying drawings. It is to be understood that the described embodiments are merely exemplary of the utility model, and not restrictive of the full scope of the utility model. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

According to an embodiment of the utility model, a control device of a flyback switching power supply is provided. Referring to fig. 1, a schematic diagram of an embodiment of the apparatus of the present invention is shown. The flyback switching power supply comprises: PFC circuits and transformers, such as the high frequency transformer T1 shown in fig. 3. The PFC circuit includes: PFC inductance and switching tube. The switch tube is the switch tube Q shown in figure 3. And the PFC inductor is used as a primary winding of the transformer.

In some embodiments, the PFC circuit further comprises: diode module and electric capacity module. A diode module such as diode D1 shown in fig. 3. A capacitive module, such as the capacitor C shown in fig. 3.

The synonym terminal of the primary winding of the transformer is connected to the anode of the diode module, and is also connected to the first connection terminal of the switching tube, such as the drain of the switching tube Q. And a second connecting end of the switch tube, such as a source electrode of the switch tube Q, is connected to the cathode of the diode module after passing through the capacitor module. And the control end of the switching tube is used for receiving the driving signal.

Fig. 2 is a schematic diagram of a power supply topology. As shown in fig. 2, an exemplary circuit of a power supply topology of a home appliance has 3 outputs. The power supply topology includes: a BOOST PFC circuit composed of a PFC inductor L, MOS, a Q2 and a diode D, and a flyback power supply circuit composed of a high-frequency transformer T1, a power switch Q1 (some analog power supply ICs have the switch Q1 built therein), a rectifier diode D1, a rectifier diode D2, a rectifier diode D3 and a filter capacitor C1 thereof, a filter capacitor C2 and a filter capacitor C3. The output end of the three-way flyback power supply circuit respectively supplies power to the load 1, the load 2 and the load 3. The output voltage Vo of the output end of the three paths of flyback power supplies is output to the grid electrode of the power switch tube Q1 through the analog power supply IC. The drain of the power switch tube Q1 is connected with the synonym terminal of the primary winding of the high-frequency transformer T1.

In the example shown in fig. 2, the primary winding of the high-frequency transformer T1 takes power from the bus bar on the rear side of the PFC circuit, and converts the dc power into ac power by controlling the power switching tube Q1. The control method in the related scheme adopts voltage and current double-loop control, and further realizes the output of driving PWM. And then, energy is transmitted to a first secondary winding, a second secondary winding and a third secondary winding of a high-frequency transformer T1 through a primary winding of the high-frequency transformer T1, high-voltage electricity is converted into low-voltage electricity through a high-frequency transformer T1 primary-secondary turn ratio setting and analog IC control switch tube Q1, and required low-voltage direct current electricity is obtained through a rectifier diode and a filter capacitor and is supplied to loads of all circuits. The number of turns of the primary winding of the high-frequency transformer T1 is N1, the number of turns of the first secondary winding of the high-frequency transformer T1 is N2, the number of turns of the second secondary winding of the high-frequency transformer T1 is N3, and the number of turns of the third secondary winding of the high-frequency transformer T1 is N4.

In the power topology shown in fig. 2, the main control unit includes: the device comprises a first comparator, a PI module, a controller, a current sensor, a sampling resistor Rs and a driving circuit. The current sensor detects the current of the source electrode of the switching tube Q2 to obtain the current I of the PFC circuit_PFC. Current I of PFC circuit_PFCAfter the voltage passes through the sampling resistor Rs, the voltage of the PFC circuit is obtained and output to a first input end of the controller. The reference voltage Uref is input to the non-inverting input end of the first comparator, the bus voltage Up of the PFC circuit is input to the inverting input end of the first comparator, and the output end of the first comparator outputs the voltage Um after passing through the PI module. The voltage Um is input to a second input of the controller. The output end of the controller outputs a voltage U1 to the inverting input end of the controller, a regulating voltage U2 is input to the non-inverting input end of the controller, and the output end of the controller is input to the grid electrode of the switching tube Q2 after passing through the driving circuit.

Fig. 3 is a schematic structural diagram of a novel power supply topology. As shown in fig. 3, the power supply topology shown in fig. 2 is improved to provide a novel power supply circuit, which includes: a BOOST PFC circuit composed of a primary inductor of the high-frequency transformer T1 (the primary winding of the high-frequency transformer T1, i.e., the inductor of the PFC circuit), a switching tube Q, and a diode D1, and a secondary winding of the high-frequency transformer T1.

In the example shown in fig. 3, a PFC inductor (i.e., an inductor of a PFC circuit) is integrated with a primary winding of the high-frequency transformer T1, the primary winding of the high-frequency transformer T1, i.e., the primary inductor of the high-frequency transformer T1, serves as the PFC inductor, the switching tube Q of the PFC circuit functions as a switching tube in the flyback power supply, the dc power is converted into the ac power by turning on or off the switching tube Q, and the energy is transmitted to the secondary side of the high-frequency transformer T1 through the primary side of the high-frequency transformer T1.

In some embodiments, the number of secondary windings of the transformer is more than one. In more than one secondary winding of the transformer, the output end of each secondary winding supplies power to a load after passing through the corresponding rectifying module and the corresponding filtering module.

In some embodiments, in more than one secondary winding of the transformer, the synonym terminal of each secondary winding is connected to the anode of the corresponding rectifier module. And the dotted end of each secondary winding is connected to the cathode of the corresponding rectifying module after passing through the capacitor module.

The example of the novel power supply circuit shown in fig. 3 has 3 outputs, and further includes: and the rectifier diode D2, the rectifier diode D3, the rectifier diode D4 and a filter capacitor C1 thereof, the filter capacitor C2 and the filter capacitor C3 form a flyback power supply circuit.

The control device of the flyback switching power supply comprises: a sampling unit and a control unit, such as a main control unit MCU shown in fig. 3.

The sampling unit is configured to sample a primary PFC current of the transformer and sample a secondary output voltage of the transformer. The primary PFC current of the transformer, e.g. the primary PFC current I of the high-frequency transformer T1_PFC. The secondary output voltage of the transformer, e.g. the secondary output voltage U of a high-frequency transformer T1_O。

In some embodiments, the sampling unit includes: the device comprises a first sampling unit and a second sampling unit.

The sampling unit is used for sampling the primary PFC current of the transformer and sampling the secondary output voltage of the transformer, and comprises:

the first sampling unit is configured to sample an operating current of the switching tube, that is, a source current of the switching tube Q, as the transformation voltageThe primary PFC current of the transformer is output in the form of voltage. In the example shown in fig. 3, the primary PFC current I of the high-frequency transformer T1 is sampled by a current sensor and a sampling resistor Rs_PFC。

The second sampling unit is configured to sample a voltage of a same-name end of a secondary winding of the transformer as a secondary output voltage of the transformer.

The control unit is configured to control a driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, so that direct current provided by a direct current power supply is converted into alternating current by controlling the switching tube to be switched on and switched off, and the alternating current is transmitted to a secondary winding of the transformer through a primary winding of the transformer to supply power to a load.

The scheme of the utility model provides a novel household appliance power supply and a control method thereof, and a PFC (power factor correction) inductor is used as the primary side of a high-frequency transformer, so that the cost of a controller is effectively reduced, and the area of a PCB (printed circuit board) is reduced. With the progress of digital power supply technology, the power supply of modern household electrical appliance controller develops digitalization, high frequency and miniaturization, and the hardware cost is also obviously reduced. The scheme of the utility model has the characteristics. The utility model also provides a control method of the power factor correction circuit of the household appliance power supply, which improves the stability of the power factor correction circuit at the input end of the circuit and the output voltage.

In some embodiments, the control unit comprises: the device comprises a first comparator, a PI controller, a second comparator and a driving circuit.

The control unit controls the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, and comprises:

the first comparator is configured to compare a reference voltage with a secondary side output voltage of the transformer to obtain a first voltage.

The PI controller is configured to perform PI processing on the first voltage to obtain a second voltage, such as the voltage Um shown in fig. 3.

The controller is configured to compare the second voltage with a primary PFC current of the transformer to obtain a third voltage, such as a voltage U1 shown in fig. 3.

The second comparator is configured to compare the third voltage with a secondary side output voltage of the transformer to obtain a driving voltage.

The driving circuit is configured to generate a control signal as a driving signal for controlling the switching tube based on the driving voltage.

In the example shown in fig. 3, control is performed using a Master Control Unit (MCU). The Main Control Unit (MCU) is based on the primary PFC current I of the high-frequency transformer T1 obtained by sampling_PFCSecondary output voltage U of high frequency transformer T1_OThe secondary side of the high-frequency transformer T1 is output with a voltage U by a first comparator_OAnd comparing the voltage with the reference output voltage Vref, and processing the obtained error through a controller to obtain the voltage Um. The PI controller forms a control deviation according to a given value and an actual output value, and linearly combines the proportion and the integral of the deviation to form a control quantity to control a controlled object.

The voltage Um is compared with the voltage of the sampling resistor Rs (PFC current sampling) by the controller, resulting in a voltage U1. By means of a second comparator, the voltage U1 is compared with the carrier voltage U2, and the switching tube Q is switched on when the voltage U1< the carrier voltage U2. On the contrary, the switching tube Q is turned off, the duty ratio of the driving signal of the switching tube Q is further adjusted through voltage-current loop control, the turn ratio of the primary side and the secondary side of the high-frequency transformer T1 is set according to the output voltage, and as can be known from the relationship between the primary side voltage and the secondary side voltage of the transformer and the number of turns: U1/U2 is N1/N2, N1 and N2 are the number of primary and secondary turns respectively, high-voltage electricity is converted into low-voltage electricity by a high-frequency transformer T1, and then required low-voltage direct current electricity is obtained through a rectifier diode D2, a rectifier diode D3, a rectifier diode D4, a filter capacitor C1, a filter capacitor C2 and a filter capacitor C3 and is supplied to loads (such as a load 1, a load 2 and a load 3), closed-loop control is achieved, and stability of a power supply topology is improved.

In the example shown in fig. 3, the main control unit controls the high-frequency transformer T1 by sampling the secondary-side output voltage Uo of the high-frequency transformer T1 and the primary-side PFC current I_PFCThe generation of driving PWM is realized through the control of the comparator (such as the first comparator, the controller and the second comparator) and the controller (such as the PI regulator), and then the on-off of the switching tube Q is controlled, so that an analog power supply IC and a PFC inductor are omitted, the cost of the controller is effectively reduced, and the area of a PCB is reduced.

In some embodiments, further comprising: the control unit is further configured to determine whether the on-time or off-time of a switching tube in the PFC circuit reaches a given time before controlling the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, and if so, control the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer. Otherwise, the secondary side output voltage of the transformer is increased according to a set increasing mode, and then the driving signal of the switching tube is controlled according to the primary side PFC current of the transformer and the secondary side output voltage of the transformer.

The flyback switching power supply works all the time, the given time is set by software, a software PFC program only performs Sampling once in a switching period, the Sampling mode becomes SSOP (Single Sampling in One period), the method needs to pay attention to the determination of Sampling points, the current peak exists at the moment of switching action of a switching tube due to inductive current, the Sampling is needed to be avoided near a switching point, otherwise, the system is unstable, and the solution is to perform Sampling at the middle moment of long switching-on or switching-off time of the switching tube, so a given time needs to be set.

Fig. 4 is a control flow diagram of a novel power supply topology. As shown in fig. 4, the control flow of the novel power supply topology includes:

step 1, firstly, judging whether the on-time or the off-time of a switch tube in the PFC circuit reaches a given time, if so, executing step 2. Otherwise, step 3 is executed.

And 2, directly reading A/D sampling data if the on-time or off-time of a switch tube in the PFC circuit reaches a given time. That is, when the predetermined time is not reached, in order to reduce the impact of the current at the time of starting, the output voltage needs to be slowly increased to the reference voltage value, and the duty ratio is continuously adjusted according to the feedback to reach the set value.

And 3, if the on-time or off-time of a switching tube in the PFC circuit does not reach the given time, slowly increasing a voltage given instruction, namely slowly increasing the output voltage to prevent voltage overshoot, reading A/D sampling data, and then executing the step 4.

Step 4, the A/D sampling data comprises a secondary side voltage Uo of a high-frequency transformer T1 and a primary side PFC current I of a high-frequency transformer T1_PFCThen, the difference between the given voltage command and the sampled voltage is sent to a controller (such as a voltage PI regulator) and output as a voltage Um, i.e., a PI regulator output voltage Um, and then step 5 is executed.

And step 5, calculating the duty ratio, then starting to update the comparison unit value (such as updating CMPR4), outputting a PWM signal to the switching tube Q, then calculating the A/D sampling time according to the duty ratio, triggering A/D sampling by using the comparison interruption of a timer, and updating the T3 CMPR.

The comparison unit value relates to the setting of the comparison register in the program, and the value can be influenced by the duty ratio, so that the value can be updated when the switching tube is turned on or off. CMPR4, T3CMRP, are the underlying settings in software.

The power supply topology shown in fig. 3 uses BOOST inductor as the primary inductor of the high frequency transformer T1, so that the power supply topology reduces one inductor. The voltage and current of the primary side and the secondary side of the high-frequency transformer T1 are used for controlling the main control unit, and the use of an analog power supply IC is reduced. Therefore, the area of the PCB can be reduced structurally, and the structure is smaller. The aim of reducing the cost can be achieved due to the reduction of the devices in cost.

Through a large number of tests, the technical scheme of the utility model is adopted, the PFC inductor of the flyback switching power supply is used as the primary winding of the high-frequency transformer, the switching tube Q of the PFC circuit has the same function as the switching tube in the flyback switching power supply, the driving signal of the switching tube Q is controlled according to the primary PFC current IPFC of the transformer and the secondary output voltage Uo of the transformer, the switching tube Q is controlled to be switched on or off, the direct current is converted into the alternating current, the energy is transmitted to the secondary side of the high-frequency transformer T1 through the primary side of the high-frequency transformer T1, the cost of the controller is effectively reduced, and the area of a PCB (printed circuit board) is reduced.

According to the embodiment of the utility model, the flyback switching power supply corresponding to the control device of the flyback switching power supply is also provided. The flyback switching power supply may include: the control device of the flyback switching power supply is described above.

Since the processes and functions implemented by the flyback switching power supply of this embodiment substantially correspond to the embodiments, principles, and examples of the foregoing devices, the description of this embodiment is not given in detail, and reference may be made to the related descriptions in the foregoing embodiments, which are not described herein again.

Through a large number of tests, the technical scheme of the utility model is adopted, the PFC inductor of the flyback switching power supply is used as the primary winding of the high-frequency transformer, the switching tube Q of the PFC circuit has the same function as the switching tube in the flyback switching power supply, the driving signal of the switching tube Q is controlled according to the primary PFC current IPFC of the transformer and the secondary output voltage Uo of the transformer, the switching tube Q is controlled to be switched on or off, the direct current is converted into the alternating current, the energy is transmitted to the secondary side of the high-frequency transformer T1 through the primary side of the high-frequency transformer T1, the closed-loop control is realized, and the stability of the power supply topology is improved.

According to an embodiment of the present invention, a method for controlling a flyback switching power supply corresponding to the flyback switching power supply is also provided, as shown in fig. 5, which is a schematic flow chart of an embodiment of the method of the present invention. The flyback switching power supply comprises: PFC circuits and transformers, such as the high frequency transformer T1 shown in fig. 3. The PFC circuit includes: PFC inductance and switching tube. The switch tube is the switch tube Q shown in figure 3. And the PFC inductor is used as a primary winding of the transformer. The control method of the flyback switching power supply comprises the following steps: step S110 and step S120.

In step S110, a primary PFC current of the transformer is sampled and a secondary output voltage of the transformer is sampled by a sampling unit. The primary PFC current of the transformer, e.g. the primary PFC current I of the high-frequency transformer T1_PFC. The secondary output voltage of the transformer, e.g. the secondary output voltage U of a high-frequency transformer T1_O。

At step S120, a control unit, such as the main control unit MCU shown in fig. 3, controls a driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, so as to convert the dc power provided by the dc power supply into ac power by controlling the switching tube to be turned on and off, and transmit the ac power to the secondary winding of the transformer through the primary winding of the transformer, so as to supply power to the load.

Fig. 3 is a schematic structural diagram of a novel power supply topology. As shown in fig. 3, the power supply topology shown in fig. 2 is improved to provide a novel power supply circuit, which includes: a BOOST PFC circuit composed of a primary inductor of the high-frequency transformer T1 (i.e., an inductor of the PFC circuit which is a primary winding of the high-frequency transformer T1), a switching tube Q, and a diode D1, and a flyback power supply circuit composed of a secondary winding of the high-frequency transformer T1, a rectifier diode D2, a rectifier diode D3, a rectifier diode D4, and a filter capacitor C1, a filter capacitor C2, and a filter capacitor C3.

In the example shown in fig. 3, the primary PFC current I of the high-frequency transformer T1 is sampled by a current sensor and a sampling resistor Rs_PFC。

In some embodiments, in step S120, a specific process of controlling the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer is performed by a control unit, which is described in the following exemplary description.

With reference to the flowchart of fig. 6 showing an embodiment of the method of the present invention, wherein the method controls the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, further described is a specific process of controlling the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer in step S120, including: step S210 to step S250.

Step S210, comparing, by a first comparator, the reference voltage with the secondary output voltage of the transformer to obtain a first voltage.

In step S220, PI processing is performed on the first voltage through a PI controller to obtain a second voltage, such as the voltage Um shown in fig. 3.

Step S230, comparing, by the controller, the second voltage with the primary PFC current of the transformer to obtain a third voltage, such as a voltage U1 shown in fig. 3.

Step S240, comparing, by a second comparator, the third voltage with the secondary output voltage of the transformer to obtain a driving voltage.

And step S250, generating a control signal as a driving signal for controlling the switching tube through a driving circuit based on the driving voltage.

In the example shown in fig. 3, control is performed using a Master Control Unit (MCU). The Main Control Unit (MCU) is based on the primary PFC current I of the high-frequency transformer T1 obtained by sampling_PFCSecondary output voltage U of high frequency transformer T1_OThe secondary side of the high-frequency transformer T1 is output with a voltage U by a first comparator_OAnd comparing the voltage with the reference output voltage Vref, and processing the obtained error through a controller to obtain the voltage Um. The voltage Um is compared with the voltage of the sampling resistor Rs (PFC current sampling) by the controller, resulting in a voltage U1. The voltage U1 is compared with the carrier voltage U2 by a second comparator when the voltage U1 is higher than the carrier voltage U2<The switching tube Q is turned on when the carrier voltage U2 is applied. On the contrary, the switching tube Q is turned off, the duty ratio of a driving signal of the switching tube Q is adjusted through voltage-current loop control, the turn ratio of the primary side and the secondary side of the high-frequency transformer T1 is set according to the magnitude of the output voltage, the high-frequency transformer T1 converts high-voltage power into low-voltage power, and the required low-voltage direct current power is obtained through the rectifier diode D2, the rectifier diode D3, the rectifier diode D4, the filter capacitor C1, the filter capacitor C2 and the filter capacitor C3 and is supplied to each load (such as a load 1, a load 2 and a load 3), so that closed-loop control is realized, and the stability of a power supply topology is improved.

In some embodiments, the above method for controlling a flyback switching power supply further includes: and determining whether the on-time or off-time of a switching tube in the PFC circuit reaches a given time or not by the control unit before controlling the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, and if so, controlling the driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer. Otherwise, the secondary side output voltage of the transformer is increased according to a set increasing mode, and then the driving signal of the switching tube is controlled according to the primary side PFC current of the transformer and the secondary side output voltage of the transformer.

And 2, directly reading A/D sampling data if the on-time or off-time of a switch tube in the PFC circuit reaches a given time.

And 3, if the on-time or off-time of a switching tube in the PFC circuit does not reach the given time, slowly increasing a voltage given instruction, reading A/D sampling data, and then executing the step 4.

Since the processes and functions implemented by the method of the present embodiment substantially correspond to the embodiments, principles, and examples of the flyback switching power supply, the description of the present embodiment is not given in detail, and reference may be made to the related descriptions in the embodiments, which are not described herein again.

Through a large number of tests, the technical scheme of the embodiment is adopted, the PFC inductor of the flyback switching power supply is used as the primary winding of the high-frequency transformer, the switching tube Q of the PFC circuit has the same function as the switching tube in the flyback switching power supply, the driving signal of the switching tube Q is controlled according to the primary PFC current IPFC of the transformer and the secondary output voltage Uo of the transformer, the switching tube Q is controlled to be switched on or off, the direct current is converted into the alternating current, and the energy is transmitted to the secondary side of the high-frequency transformer T1 through the primary side of the high-frequency transformer T1; therefore, the PFC inductor of the flyback switching power supply is used as the primary winding of the high-frequency transformer, so that the structure of the flyback switching power supply can be effectively simplified.

In summary, it is readily understood by those skilled in the art that the advantageous modes described above can be freely combined and superimposed without conflict.

The above description is only an example of the present invention, and is not intended to limit the present invention, and it is obvious to those skilled in the art that various modifications and variations can be made in the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A control device of a flyback switching power supply is characterized in that the flyback switching power supply comprises: a PFC circuit and a transformer; the PFC circuit includes: a PFC inductor and a switching tube; the PFC inductor is used as a primary winding of the transformer; the control device of the flyback switching power supply comprises: a sampling unit and a control unit; wherein the content of the first and second substances,

the sampling unit is configured to sample a primary PFC current of the transformer and sample a secondary output voltage of the transformer;

the control unit is configured to control a driving signal of the switching tube according to the primary PFC current of the transformer and the secondary output voltage of the transformer, so that direct current provided by a direct current power supply is converted into alternating current by controlling the switching tube to be switched on and switched off, and the alternating current is transmitted to a secondary winding of the transformer through a primary winding of the transformer.

2. The apparatus of claim 1, wherein the PFC circuit further comprises: a diode module and a capacitor module; wherein the content of the first and second substances,

the synonym end of the primary winding of the transformer is connected to the anode of the diode module and is also connected to the first connecting end of the switching tube; the second connecting end of the switch tube is connected to the cathode of the diode module after passing through the capacitor module; and the control end of the switching tube is used for receiving the driving signal.

3. The control device of the flyback switching power supply of claim 2, wherein the number of the secondary windings of the transformer is more than one; in more than one secondary winding of the transformer, the output end of each secondary winding supplies power to a load after passing through the corresponding rectifying module and the corresponding filtering module.

4. The control device of the flyback switching power supply of claim 3, wherein in more than one secondary winding of the transformer, a synonym terminal of each secondary winding is connected to an anode of a corresponding rectifier module; and the dotted end of each secondary winding is connected to the cathode of the corresponding rectifying module after passing through the capacitor module.

5. The control device of the flyback switching power supply according to any one of claims 1 to 4, wherein the sampling unit includes: a first sampling unit and a second sampling unit;

the first sampling unit is configured to sample the working current of the switching tube to serve as the primary PFC current of the transformer, and the primary PFC current of the transformer is output in the form of voltage;

6. The control device of the flyback switching power supply according to any one of claims 1 to 4, wherein the control unit includes: the device comprises a first comparator, a PI controller, a second comparator and a driving circuit;

the first comparator is configured to compare a reference voltage with a secondary side output voltage of the transformer to obtain a first voltage;

the PI controller is configured to perform PI processing on the first voltage to obtain a second voltage;

the controller is configured to compare the second voltage with a primary PFC current of the transformer to obtain a third voltage;

the second comparator is configured to compare the third voltage with a secondary side output voltage of the transformer to obtain a driving voltage;

7. The control device of the flyback switching power supply according to any one of claims 1 to 4, further comprising:

the control unit is further configured to determine whether the on-time or off-time of a switching tube in the PFC circuit reaches a given time, and if so, control a driving signal of the switching tube according to a primary PFC current of the transformer and a secondary output voltage of the transformer; otherwise, the secondary side output voltage of the transformer is increased according to a set increasing mode, and then the driving signal of the switching tube is controlled according to the primary side PFC current of the transformer and the secondary side output voltage of the transformer.

8. A flyback switching power supply, comprising: the control device of the flyback switching power supply of any of claims 1 to 7.