TWM561363U - Switching power supply circuit - Google Patents

Abstract

A switching power supply circuit is provided, including an AC input rectification circuit, a flyback switching transformer, a first control chip, a second control chip, a pulse transfer circuit, and a secondary side rectification circuit. Wherein: the second terminal of the flyback switching transformer is connected to the first terminal of the power switch, the third terminal is used as an output end of the switching power supply circuit, and the fourth terminal is connected to the first terminal of the secondary side rectifier circuit; the first control chip The first terminal is connected to the second terminal of the power switch, the second terminal is connected to the first terminal of the pulse transmission circuit, the third terminal is connected to the ground, and the second terminal of the pulse transmission circuit is connected to the first terminal of the second control chip The third terminal is connected to the ground, the fourth terminal is grounded; the second terminal of the second control chip is grounded; the first terminal of the secondary rectifier circuit is connected to the fourth terminal of the flyback switch transformer, and the second terminal is grounded.

Description

Switching power supply circuit

The utility model relates to the field of circuits, and more particularly to a switching power supply circuit.

In recent years, as portable screens such as smart phones, tablets, and notebook computers have become larger and faster, it is necessary to increase the battery capacity of the portable device to maintain or extend the portable type. The time of use of the device. However, as battery capacity increases, battery charging time increases dramatically, which is what most users of portable devices do not want to see.

In order to maintain the battery charging time or shorten the battery charging time, it is necessary to increase the output power of the charger and the adapter. Fast charging protocols such as those issued by Qualcomm, Huawei Technologies, and Taiwan MediaTek, and power supply voltage regulation protocols such as PD2.0 and PD3.0, have emerged with the emergence of such demands. In addition to requiring a variable output voltage, the agreement requires higher average efficiency and a smaller form factor, so synchronous rectification control is required on the secondary side.

At present, the charger and the adapter basically adopt the first control scheme shown in FIG. 1 or the second control scheme shown in FIG. 2. In the control schemes shown in FIGS. 1 and 2, when the load is instantaneously loaded or de-loaded, the synchronous rectification control of the secondary side may cause the primary side and the secondary side of the flyback switching transformer to be simultaneously turned on, thereby Will increase the risk of damage to the switching power supply circuit.

[Creation content]

In view of one or more of the problems described above, the present invention provides a novel switching power supply circuit.

A switching power supply circuit according to an embodiment of the present invention includes an AC input rectification circuit, a flyback switching transformer, a first control chip, a second control chip, a pulse transmission circuit, and a secondary side rectification circuit, wherein: the AC input rectification circuit The first terminal and the second terminal are used for connecting two ends of the alternating current power source, the third terminal is connected with the first terminal of the flyback switching transformer, the fourth terminal is connected to the ground; the first terminal of the flyback switching transformer and the alternating current input rectifier circuit The third terminal is connected, the second terminal is connected to the first terminal of the power switch, the third terminal is used as an output end of the switching power supply circuit, and the fourth terminal is connected to the first terminal of the secondary side rectifier circuit; The first terminal is connected to the second terminal of the power switch, the second terminal is connected to the first terminal of the pulse transmission circuit, the third terminal is connected to the ground; the first terminal of the pulse transmission circuit is connected to the second terminal of the first control chip, The second terminal is connected to the first terminal of the second control chip, the third terminal is connected to the ground, the fourth terminal is grounded; and the second control chip is A second terminal of the pulse transmitting terminal circuit, a second terminal connected to ground; and the first terminal of the secondary side of the rectifier circuit and the fourth terminal of the flyback transformer of the flyback switch, the second terminal is grounded.

The switching power supply circuit according to the embodiment of the present invention can avoid the occurrence of simultaneous conduction of the primary side and the secondary side of the flyback switching transformer.

300, 400, 400-A, 400-B‧‧‧ switching power supply circuit

310, 310-A, 310-B‧‧‧ secondary side rectifier circuit

302‧‧‧Input rectifier circuit

304‧‧‧First Control Wafer

306‧‧‧Second control chip

308‧‧‧Pulse transmission circuit

324‧‧‧Output voltage feedback circuit

T1‧‧‧Return switch transformer

Q1‧‧‧Power switch

312‧‧‧Electromagnetic interference filter circuit

314‧‧‧Overshoot absorption circuit

316‧‧‧Power limit circuit

318‧‧‧Output filter circuit

320‧‧‧current sampling circuit

322‧‧‧Voltage sampling circuit

A‧‧‧chip start pin, pin

B‧‧‧Wafer grounding pin, pin

C‧‧‧pulse receiving pin, pin

D‧‧‧Power limit pin, pin

E‧‧‧Power tube driver pin, pin

F‧‧‧Protection foot, pin

326‧‧‧Wafer compensation loop

328‧‧‧ wafer power supply circuit

330‧‧‧ wafer start-up circuit

332‧‧‧System Protection Circuit

G‧‧‧current sampling pin, pin (third terminal)

I‧‧‧voltage compensation pin, pin (seventh terminal)

L‧‧‧Voltage sampling pin, pin (sixth terminal)

H‧‧‧pulse launch pin, pin (first terminal)

K‧‧‧ wafer grounding pin, pin (second terminal)

M‧‧‧ voltage sensing feet, pins (fourth terminal)

J‧‧‧Voltage sampling pin, pin (fifth terminal)

N‧‧‧Reciprocating drive pin, pin (eighth terminal)

R9, R10, R1‧‧‧ resistance

The present invention can be better understood from the following description of the embodiments of the present invention with reference to the accompanying drawings, wherein FIG. 1 is a block diagram showing a conventional switching power supply circuit based on a first control scheme; A block diagram of a conventional switching power supply circuit based on a second control scheme; FIG. 3 is a circuit diagram of a switching power supply circuit according to a first embodiment of the present invention; FIGS. 4A and 4B illustrate A circuit diagram of two specific implementations of the switching power supply circuit of the second embodiment of the present invention; and FIG. 5 is a schematic block diagram of the internal functional module of the first control chip shown in the fourth embodiment of FIG. 4A-4B; Figure 6 shows the internal functional module of the second control chip shown on the way to the 4A-4B a first schematic block diagram; FIG. 7 shows a second schematic block diagram of the internal functional module of the second control wafer shown in the middle of FIG. 4A-4B; FIG. 8 shows the fourth shown in FIG. 4A-4B. The third schematic frame of the internal function module of the second control chip; FIG. 9 shows a fourth schematic block diagram of the internal function module of the second control chip shown in FIG. 4A-4B; 10A Figures to 10D show various solutions of the electromagnetic interference filter circuit shown in Figs. 4A-4B; FIGS. 11A to 11D show the wafer start circuit and wafer power supply shown in Figs. 4A-4B. Various connections of the circuit; FIGS. 12A to 12H show various connections of the overshoot absorption circuit shown in FIG. 4A-4B; FIGS. 13A to 13F show the 4A-4B diagram. Various connections of the second rectifier circuit shown; FIGS. 14A and 14B illustrate various connections of the output filter circuit shown in FIGS. 4A-4B; FIGS. 15A and 15B illustrate the Various connections of the current sampling circuit shown in FIGS. 4A-4B; FIGS. 16A to 16C show various connections of the pulse transfer circuit shown in FIGS. 4A-4B; FIGS. 17A and 17B show Various connection of voltage sampling circuit shown in 4A-4B.

Features and exemplary embodiments of various aspects of the invention are described in detail below. In the following detailed description, numerous specific details are set forth It will be apparent to those skilled in the art, however, that the invention may be practiced without some of these details. The following description of the embodiments is merely provided to provide a better example of the present invention by showing an example of the present invention. Understanding. The present invention is in no way limited to any of the specific arrangements set forth below, but without departing from the spirit and scope of the invention. The structures and techniques are not shown in the drawings and the following description in order to avoid unnecessary obscuring the present invention.

Fig. 3 is a circuit diagram showing a switching power supply circuit according to a first embodiment of the present invention. As shown in FIG. 3, the switching power supply circuit 300 includes an AC input rectification circuit 302, a first control chip 304, a second control chip 306, a pulse transfer circuit 308, a secondary side rectification circuit 310, and a flyback switching transformer T1, wherein :

The AC input rectifying circuit 302 has four terminals, wherein the first terminal and the second terminal are used to connect both ends of the AC power source, the third terminal is connected to the first terminal of the flyback switching transformer T1, and the fourth terminal is connected to the ground.

The flyback switching transformer T1 has four terminals, wherein the first terminal is connected to the third terminal of the AC input rectifying circuit 302, the second terminal is connected to the first terminal of the power switch Q1, and the third terminal is used as the switching power supply circuit 300. At the output end, the fourth terminal is connected to the first terminal of the secondary side rectifying circuit 310.

The first control wafer 304 has three terminals, wherein the first terminal is connected to the second terminal of the power switch Q1, the second terminal is connected to the first terminal of the pulse transfer circuit 308, and the third terminal is connected to the ground.

The pulse transfer circuit 308 has four terminals, wherein the first terminal is connected to the second terminal of the first control chip 304, the second terminal is connected to the first terminal of the second control chip 306, and the third terminal is connected to the ground, fourth The terminal is grounded.

The second control wafer 306 has two terminals, wherein the first terminal is coupled to the second terminal of the pulse transfer circuit 308 and the second terminal is coupled to ground.

The secondary side rectifying circuit 310 has two terminals, wherein the first terminal is connected to the fourth terminal of the flyback flyback switching transformer T1, and the second terminal is grounded.

In the embodiment shown in Fig. 3, the third terminal of the power switch Q1 is connected to ground.

4A and 4B illustrate a second embodiment in accordance with the present invention A circuit diagram of two specific implementations of a switching power supply circuit. A switching power supply circuit according to a second embodiment of the present invention will be described in detail below with reference to FIGS. 4A and 4B.

As shown in FIG. 4A to FIG. 4B, the power switch circuit 400 (the switching power supply circuits 400-A and 400-B collectively referred to as the power switch circuit 400) includes an AC input rectification circuit 302, a first control chip 304, and a second control. The wafer 306, the pulse transfer circuit 308, the secondary side rectification circuit 310 (the secondary side rectification circuits 310-A and 310-B are collectively referred to as the secondary side rectification circuit 310), and the flyback switching transformer T1 may further include electromagnetic interference. Filter circuit 312, overshoot absorbing circuit 314, power limiting circuit 316, output filter circuit 318, current sampling circuit 320, voltage sampling circuit 322, output voltage feedback circuit 324, wafer compensation loop 326, chip power supply circuit 328, wafer start circuit 330. One or more circuits in system protection circuit 332, wherein: The electromagnetic interference filter circuit 312 has three terminals, wherein the first terminal and the second terminal are respectively connected to the third terminal and the fourth terminal of the AC input rectifying circuit 302, and the third terminal and the first terminal of the flyback switching transformer T1 ( That is, the first terminal of the primary winding of the flyback switching transformer T1 is connected. At this time, the third terminal of the AC input rectifying circuit 302 is no longer connected to the first terminal of the flyback switching transformer T1.

The overshoot absorbing circuit 314 has two terminals, wherein: the first terminal and the second terminal respectively correspond to the first terminal and the second terminal of the flyback switching transformer T1 (ie, the first terminal of the primary winding of the flyback switching transformer T1 and The second terminal) is connected.

The power limiting circuit 316 has two terminals, wherein the first terminal is connected to the third terminal of the power switch Q1 and the fourth terminal of the first control chip 304, and the second terminal is connected to ground. At this time, the third terminal of the power switch Q1 is no longer connected to the ground.

The output filter circuit 318 has two terminals, wherein: the first terminal is connected to the third terminal of the flyback switching transformer T1 (ie, the first terminal of the secondary winding of the flyback switching transformer T1), and the second terminal and the secondary side The second terminal connection of the rectifier circuit 310 (the second rectifier circuits 310-A and 310-B in FIGS. 4A and 4B are two implementations of the secondary side rectifier circuit 310).

The current sampling circuit 320 has three terminals, wherein: the first terminal and the fourth terminal of the flyback switching transformer T1 (ie, the second terminal of the primary winding of the flyback switching transformer T1) and the second rectifier circuit 310 One terminal is connected, the second terminal is connected to the third terminal of the second control wafer 306, and the third terminal is grounded.

The voltage sampling circuit 322 has three terminals, wherein: the first terminal is connected to the third terminal of the flyback switching transformer T1 and the fourth terminal of the second control chip 306, and the second terminal is connected to the fifth terminal of the second control wafer 306. The third terminal is grounded.

The output voltage feedback circuit 324 has three terminals, wherein: the first terminal is connected to the third terminal of the flyback switch transformer T1 and the fourth terminal of the second control chip 306, and the second terminal is connected to the sixth terminal of the second control chip 306. Connected, the third terminal is grounded.

The wafer compensation loop 326 has two terminals, wherein the first terminal is coupled to the seventh terminal of the second control wafer 306 and the second terminal is coupled to ground.

The chip power supply circuit 328 has three terminals, wherein: the first terminal is connected to the fifth terminal of the flyback switching transformer T1 (ie, the first terminal of the auxiliary winding of the flyback switching transformer T1), and the second terminal and the first control chip The fifth terminal of the 306 is connected, and the third terminal is connected to the ground. At this time, the sixth terminal of the flyback switching transformer T1 (ie, the second terminal of the auxiliary winding of the flyback switching transformer T1) is connected to the ground.

The wafer start-up circuit 330 has two terminals, wherein the first terminal is connected to the first terminal of the flyback switching transformer T1, and the second terminal is connected to the second terminal of the wafer power supply circuit 328 and the fifth terminal of the second control wafer 304.

The system protection circuit 332 has three terminals, wherein: the first terminal is connected to the first terminal of the wafer power supply circuit 328 and the fifth terminal of the flyback switching transformer T1, and the second terminal is connected to the sixth terminal of the first control chip 304, The third terminal is connected to the ground.

In some embodiments, the switching power supply circuit 400 can include both the output voltage feedback circuit 324 and the wafer compensation circuit 326, and may not include any of them. That is, the output voltage feedback circuit 324 and the wafer compensation loop 326 are paired circuits that may or may not be present in the switching power supply circuit 400.

In some embodiments, the switching power supply circuit 400 may include only the current sampling circuit 320, and may also include the current sampling circuit 320 and the voltage sampling circuit 322. By. That is, the voltage sampling circuit 322 is associated with the current sampling circuit 320, and the switching power supply circuit 400 can further include the voltage sampling circuit 322 under the condition of including the current sampling circuit 320.

In some embodiments, when the flyback switching transformer T1 includes an auxiliary winding, the switching power supply circuit 400 may further include a wafer power supply circuit 328, and may also include a wafer starting circuit 330 and a system protection circuit 332 while including the wafer power supply circuit 328. One or two circuits in the middle. Specifically, in the case where the switching power supply circuit 400 further includes the wafer power supply circuit 328 without including the wafer starting circuit 330 and/or the system protection circuit 332, the first terminal of the wafer power supply circuit 328 and the fifth terminal of the flyback switching transformer T1 (ie, the first terminal of the auxiliary winding of the flyback switching transformer T1 is connected), the second terminal is connected to the fifth terminal of the first control wafer 304, the third terminal is connected to the ground; and the switching power supply circuit 400 includes the wafer power supply circuit 328. In the case where the wafer start-up circuit 330 and/or the system protection circuit 332 are also included, the connection relationship between them is as shown in FIGS. 4A and 4B.

It should be noted that the circuit diagrams shown in FIG. 4A and FIG. 4B differ only in that the second rectifier circuit 310-A in the fourth AA is implemented by the diode, and the second rectifier circuit 310 in the fourth lane. -B is implemented by a power switch.

Fig. 5 is a schematic block diagram showing the internal functional modules of the first control wafer shown in Figs. 4A-4B. As shown in FIG. 5, the first control chip 304 includes an internal startup circuit, a protection signal detection circuit, a pulse width modulation (PWM) circuit, an overcurrent protection circuit, a logic control circuit, and a first driving circuit. , wherein: the internal startup circuit is connected to the pin A (ie, the fifth terminal) of the first control chip 304, the first driving circuit, and the logic control circuit; and the protection signal detecting circuit and the pin F of the first control chip 304 ( That is, the sixth terminal is connected to the logic control circuit; the pulse width modulation circuit is connected to the pin C (ie, the second terminal) of the first control chip 304 and the logic control circuit; the overcurrent protection circuit and the first control chip The pin D of the 304 (ie, the fourth terminal) is connected to the logic control circuit; the logic control circuit is connected to the internal startup circuit, the protection signal detection circuit, the pulse width modulation circuit, the overcurrent protection circuit, and the first driving circuit; The first driving circuit is connected to the pin E (ie, the first terminal) of the first control wafer 304, the internal starting circuit, and the logic control circuit; and the pin B (ie, the third terminal) of the first control chip 304 is connected Reference Ground.

In some embodiments, pins A through B of the first control wafer 310 Respectively: a wafer enable pin (ie, pin A) coupled to an internal startup circuit for controlling activation and deactivation of the first control die 304; a wafer ground pin (ie, pin B) as the first control die 304 Reference ground; a pulse receiving pin (ie, pin C) coupled to the pulse width modulation circuit for receiving a pulse signal transmitted from the second control chip 306 via the pulse transfer circuit 308; a power limiting pin ( That is, the pin D) is connected to the overcurrent protection circuit for detecting the primary side deflection group current of the flyback switching transformer T1, and is limited when the voltage on the primary side current sampling resistor of the flyback switching transformer T1 reaches a set threshold value. The maximum power of the switching power supply circuit, or enter the protection state; the power tube driving pin (ie, the pin E) is used to drive the power switch Q1 to be turned on or off according to the pulse signal from the logic control circuit; the protection pin (ie, the pin F) And connected to the system protection circuit for detecting the output voltage of the switching power supply circuit, and implementing overvoltage (undervoltage) protection and/or short circuit protection according to the detected output voltage.

Figures 6 through 9 show schematic block diagrams of various examples of internal functional modules of the second control wafer shown in Figures 4A-4B. The second control wafer shown in Figs. 4A-4B will be described in detail below with reference to Figs. 6 to 9.

In some embodiments, as shown in FIG. 6, in the case where the second rectifying circuit 310 in the power switch circuit 400 is implemented by a diode and the voltage sampling circuit 400 does not include a voltage sampling circuit, the second control chip 306 includes an on-chip current sampling circuit, a sawtooth wave generating circuit, a comparator, a proportional circuit, an operational amplifier, and a second driving circuit, wherein: the on-chip current sampling circuit and the pin G of the second control chip 306 (ie, the third The terminal is connected to the sawtooth generating circuit; the sawtooth generating circuit is connected to the on-chip current sampling circuit and the comparator; the comparator and the sawtooth generating circuit, the proportional circuit, and the second driving circuit are connected; the proportional circuit and the second control chip 306 Pin I (ie, the seventh terminal), the operational amplifier, and the comparator connection; the operational amplifier and the second control chip 306 pin L (ie, the sixth terminal) and the pin I (ie, the seventh terminal), the predetermined voltage source, and the proportional circuit connection; the second drive circuit is coupled to the pin H (ie, the first terminal) of the comparator and the second control chip 306; the second control chip 306 is referenced The pin K (ie, the second terminal) is grounded; the pin M of the second control wafer 306 (ie, the fourth terminal) is a chip power supply and a voltage detection pin.

In some embodiments, as shown in FIG. 7, in the case where the second rectifier circuit 310 in the power switch circuit 400 is implemented by a diode and the voltage sampling circuit 400 includes a voltage sampling circuit, the second control wafer 306 In addition to including an on-chip current sampling circuit, a sawtooth wave generating circuit, a comparator, a proportional circuit, an operational amplifier, and a second driving circuit, an on-chip voltage sampling circuit is further included, wherein: the on-chip voltage sampling circuit and the second control chip 306 The pin J (ie, the fifth terminal) is connected to the sawtooth wave generating circuit; the on-chip current sampling circuit is connected to the pin G (ie, the third terminal) of the second control chip 306 and the sawtooth wave generating circuit; the sawtooth wave is generated The circuit is coupled to the on-chip voltage sampling circuit, the on-chip current sampling circuit, and the comparator; the comparator is coupled to the sawtooth generation circuit, the proportional circuit, and the second drive circuit; the proportional circuit is coupled to the pin I of the second control chip 306 ( That is, the seventh terminal), the operational amplifier, and the comparator are connected; the operational amplifier and the second control chip 306 have the pin L (ie, the sixth terminal) and the pin I (ie, the first a terminal), a predetermined voltage source, and a proportional circuit connection; the second driver circuit is coupled to the pin H (ie, the first terminal) of the comparator and the second control chip 306; and the pin K of the second control chip 306 (ie, The second terminal) is grounded.

In some embodiments, as shown in FIG. 8, in the case where the second rectifier circuit 306 in the power switch circuit 400 is implemented by a power switch and the voltage sampling circuit 400 does not include a voltage sampling circuit, the second control chip 306 In addition to including an on-chip current sampling circuit, a sawtooth wave generating circuit, a comparator, a proportional circuit, an operational amplifier, and a second driving circuit, a third driving circuit is further included, wherein: the third driving circuit and the second control chip 306 are pinned N (ie, the eighth terminal) is connected and connected to the second driving circuit via the inverter, and the connection relationship between the other circuits is the same as in FIG. 6, and details are not described herein again.

In some embodiments, as shown in FIG. 9, in the case where the secondary side rectifying circuit 306 in the power switch circuit 400 is implemented by a power switch and the voltage sampling circuit 400 includes a voltage sampling circuit, the second control chip 306 In addition to including on-chip voltage sampling circuit, on-chip current sampling circuit, sawtooth wave generating circuit, comparator, proportional circuit, operational amplifier, And a third driving circuit in addition to the second driving circuit, wherein: the third driving circuit is connected to the pin N (ie, the eighth terminal) of the second control chip 306 and is connected to the second driving circuit via the inverter, and the other The connection relationship between the circuits is the same as in FIG. 7, and will not be described again here.

In some embodiments, the output signal of the on-chip current sampling circuit controls the rising slope of the sawtooth wave generated by the sawtooth wave generating circuit, that is, the current sampled by the current sampling circuit 320 is associated with the rising slope of the sawtooth wave generated by the sawtooth wave generating circuit. The output signal of the on-chip voltage sampling circuit controls the falling slope of the sawtooth wave generated by the sawtooth wave generating circuit, that is, the voltage sampled by the voltage sampling circuit 322 is associated with the falling slope of the sawtooth wave generated by the sawtooth wave generating circuit.

In some embodiments, the pins G to N of the second control wafer 306 are respectively: a current sampling pin (ie, a pin G) for passing during the turn-on of the power switch Q1 on the primary side of the power switching transformer T1. The combination of the resistor R9 or R9 and the resistor R10 indirectly detects the magnitude of the current on the primary side of the power switching transformer 1, and sets the rising slope of the sawtooth wave generating circuit; the pulse emitting pin (ie, pin H) is used for transmission via the pulse The circuit transmits a pulse signal to the first control chip, the pulse signal is used to control the on and off of the power switch Q1; the voltage compensation pin (ie, pin I) is used to adjust the loop of the switching power supply circuit to have sufficient phase margin And a gain margin; the voltage sampling pin (ie, pin J) is used to set the falling slope of the sawtooth wave generating circuit during the power switch Q1 of the primary side of the power switching transformer 1, thereby supporting the switching power supply circuit to operate at the break Continued Disconinuous Conducing Mode (DCM) state or Coninuous Conducing Mode (CCM) state. When the switching power supply circuit does not include the voltage sampling circuit, the pin may not exist or be left floating; the chip grounding pin (ie, pin K) serves as the reference ground for the secondary side control chip; the voltage sampling pin (ie, the pin L) ), connected to the output voltage feedback circuit by the closed-loop stable output voltage of the operational amplifier; The chip power supply and voltage sensing pin (ie, pin M) is used to power the second control chip while sensing the output voltage of the switching power supply circuit, and in some applications, the output capacitance in the output filter circuit can be quickly discharged. Connected to the output voltage; rectified drive pin (ie, pin N): used to drive the secondary side rectifier circuit to operate. When the secondary side rectification circuit is implemented by a diode, the foot may not exist or be left floating.

The working principle of the second control chip 306 is as follows: the output voltage feedback circuit sends the voltage on the voltage dividing resistor to the inverting input terminal of the operational amplifier, and obtains the output voltage of the operational amplifier through the compensation network; the output voltage of the operational amplifier passes through a proportional circuit regulator that compares the output of the sawtooth generator to generate a pulse width modulation (PWM) control signal; the PWM control signal is transmitted to the pulse transfer pin through the second driver; and the PWM control signal is transmitted to the pulse transfer circuit to The first control wafer.

In the conventional switching power supply circuit, the on and off of the power switch on the primary side of the flyback switching transformer 1 is controlled by the first control chip, and the on and off of the power switch that realizes synchronous rectification on the secondary side is controlled by the second control chip. The primary side and the secondary side cannot be uniformly coordinated, resulting in simultaneous conduction of the primary side and the secondary side. In the switching power supply circuit according to the embodiment of the present invention, the entire switching power supply circuit is controlled by the secondary side, so that it is possible to effectively avoid the simultaneous conduction of the primary side and the secondary side.

In some embodiments, the AC input rectification circuit includes a fuse (WIRE FUSE) and a rectifying diode, primarily for rectifying the AC voltage. Here, the number of rectifying diodes is at least one and at most eight; the fuse can be replaced by a fuse resistor, a wirewound resistor, or an inductor.

In some embodiments, the electromagnetic interference filter circuit includes an inductor, a high voltage electrolytic capacitor, and an electrostatic discharge (ESD) discharge resistor, mainly for suppressing electromagnetic interference and post-rectification filtering. Depending on the application, it can include two inductors, including a common-mode inductor; high-voltage electrolytic capacitors can also be used alone; ESD discharge resistor R1 can be used in some cases. 10A to 10D show various connections of the electromagnetic interference filter circuit, and R1 is an ESD discharge resistor, which can be connected in series and/or in parallel to achieve the desired resistance value, or can be eliminated.

In some embodiments, the wafer startup circuit and the wafer power supply circuit have four connections depending on different power supply modes. 11A through 11D illustrate various connections of the wafer start-up circuit and the wafer power supply circuit.

In some embodiments, the overshoot absorbing circuit includes an absorbing resistor, an absorbing capacitor, and a unidirectional diode, and FIGS. 12A through 12H illustrate various connections of the overshoot absorbing circuit.

In some embodiments, the secondary side rectification circuit includes a diode, a power switch, or a combination of a diode and a power switch. Fig. 13A to Fig. 13F show various connections of the secondary side rectifying circuit.

In some embodiments, the output filter circuit includes a filter capacitor and an output dummy load. For different output ripple requirements, the output filter circuit can add a π-type filter circuit or a common-mode filter circuit. Figures 14A and 14B show various connections of the output filter circuit.

In some embodiments, the current\sampling circuit includes a resistor divider circuit coupled to the secondary winding of the flyback switching transformer 1 or a single resistor. Figures 15A and 15B illustrate various connections of the current sampling circuit.

In some embodiments, the wafer compensation loop includes a combination of a resistor and a capacitor, and the output voltage feedback circuit includes a resistor divider circuit coupled to the voltage output of the switching power supply circuit.

In some embodiments, the pulse transfer circuit can be implemented by a Hall effect implemented communication circuit, transformer, or optocoupler device to transfer the pulse signal from the second control wafer to the first control wafer. Here, the transformer that implements the pulse transfer circuit may be a transformer with a magnetic core or a transformer with a hollow core. Figures 16A through 16C illustrate various connections of the pulse transfer circuit.

In some embodiments, the voltage sampling circuit includes a resistor divider circuit or a single resistor coupled to the voltage output of the switching power supply circuit. 17A and 17B illustrate various connections of voltage sampling circuit 332.

Compared with the conventional switching power supply circuit, the switching power supply circuit according to the embodiment of the present invention has low cost, high efficiency, small number of components, and can avoid the flyback switch The case where the primary side and the secondary side of the transformer are simultaneously turned on.

The present invention may be embodied in other specific forms without departing from the spirit and essential characteristics. The present embodiments are to be considered in all respects as illustrative and not restrict All changes within the scope of the invention are thus included in the scope of the present invention.

Claims (18)

A switching power supply circuit includes an AC input rectification circuit, a flyback switching transformer, a first control chip, a second control chip, a pulse transmission circuit, and a second rectification circuit, wherein: the first terminal and the first of the AC input rectification circuit Two terminals are connected to two ends of the AC power source, a third terminal is connected to the first terminal of the flyback switch transformer, and a fourth terminal is connected to the ground; the first terminal of the flyback switch transformer is rectified with the AC input a third terminal of the circuit is connected, a second terminal is connected to the first terminal of the power switch, a third terminal is used as an output end of the switching power supply circuit, and a fourth terminal is connected to the first terminal of the second rectifier circuit; a first terminal of the first control chip is connected to the second terminal of the power switch, a second terminal is connected to the first terminal of the pulse transmission circuit, and a third terminal is connected to the ground; the first of the pulse transmission circuit The terminal is connected to the second terminal of the first control chip, the second terminal is connected to the first terminal of the second control chip, and the third terminal is connected to the ground, The terminal is grounded; the first terminal of the second control chip is connected to the second terminal of the pulse transfer circuit, the second terminal is grounded; and the first terminal of the second rectifier circuit and the first switch of the flyback switch The four terminals are connected and the second terminal is grounded. The switching power supply circuit of claim 1, wherein the pulse transfer circuit is a communication circuit implemented by a Hall effect, the circuit transmitting a pulse signal from the second control wafer to the first control wafer. The switching power supply circuit of claim 1, wherein the pulse transfer circuit is a transformer that transmits a pulse signal from the second control wafer to the first control wafer. The switching power supply circuit of claim 3, wherein the transformer is a transformer with a magnetic core. The switching power supply circuit of claim 3, wherein the transformer is a hollow core transformer. The switching power supply circuit of claim 1, wherein the pulse transfer circuit is an optocoupler A device that transmits a pulse signal from the second control wafer to the first control wafer. The switching power supply circuit of claim 1, further comprising: an electromagnetic interference filter circuit, wherein the first terminal and the second terminal are respectively connected to the third terminal and the fourth terminal of the AC input rectifier circuit, and the third terminal and the The first terminal of the flyback switching transformer is connected, and at this time, the third terminal of the AC input rectifier circuit is no longer connected to the first terminal of the flyback switch transformer. The switching power supply circuit according to any one of claims 1 to 7, further comprising: an overshoot absorption circuit, wherein the first terminal and the second terminal are respectively connected to the first terminal and the second terminal of the flyback switch transformer . The switching power supply circuit of claim 8, further comprising: a power limiting circuit, wherein the first terminal is connected to the third terminal of the power switch and the fourth terminal of the first control chip, and the second terminal is connected to the ground . The switching power supply circuit of claim 8, further comprising: an output filter circuit, the first terminal of which is connected to the third terminal of the flyback switch transformer, and the second terminal is connected to the second terminal of the second rectifier circuit . The switching power supply circuit of claim 8, further comprising: a current sampling circuit, wherein the first terminal is connected to the fourth terminal of the flyback switch transformer and the first terminal of the second rectifier circuit, and the second terminal is The third terminal of the second control chip is connected, and the third terminal is grounded. The switching power supply circuit of claim 11, further comprising: a voltage sampling circuit, wherein the first terminal is connected to the third terminal of the flyback switch transformer and the fourth terminal of the second control chip, and the second terminal is The fifth terminal of the second control chip is connected, and the third terminal is grounded. The switching power supply circuit of claim 11, wherein the second control chip comprises a sawtooth wave generating circuit, and the current sampled by the current sampling circuit is associated with a rising slope of a sawtooth wave generated by the sawtooth wave generating circuit . The switching power supply circuit of claim 12, wherein the second control chip comprises a sawtooth wave generating circuit, and the voltage sampled by the voltage sampling circuit generates electricity with the sawtooth wave The falling slope of the sawtooth wave generated by the path is associated. The switching power supply circuit of claim 8, further comprising: an output voltage feedback circuit, the first terminal of which is connected to the third terminal of the flyback switch transformer and the fourth terminal of the second control chip, the second terminal Connected to the sixth terminal of the second control wafer, the third terminal is grounded; and the wafer compensation loop has a first terminal connected to the seventh terminal of the second control wafer and a second terminal grounded. The switching power supply circuit of claim 8, further comprising: a wafer power supply circuit, the first terminal of which is connected to the fifth terminal of the flyback switch transformer, and the second terminal is connected to the fifth terminal of the first control chip The third terminal is connected to the ground. The switching power supply circuit of claim 16, further comprising: a wafer starting circuit, the first terminal of which is connected to the first terminal of the flyback switching transformer, the second terminal and the second terminal of the chip power supply circuit The fifth terminal of the first control wafer is connected. The switching power supply circuit of claim 17, further comprising: a system protection circuit, wherein the first terminal is connected to the first terminal of the chip power supply circuit and the fifth terminal of the flyback switch transformer, and the second terminal The sixth terminal of the first control wafer is connected, and the third terminal is connected to the ground.