TWM455297U - Reverse-exciting type switch power supply circuit - Google Patents

Abstract

The utility model discloses a fly-back switch power supply circuit. The fly-back switch power supply circuit comprises an AC (Alternating Current) rectifying circuit, an electromagnetic interference filtering circuit, a starting circuit, a fly-back switch circuit, an output rectifying filtering circuit, a control circuit and a feedback circuit. The input end of the electromagnetic interference filtering circuit is connected with the output end of the AC rectifying circuit. The input end of the starting circuit is connected with the output end of the electromagnetic interference filtering circuit. The input end of the fly-back switch circuit is connected with the output end of the starting circuit. The output end of the fly-back switch circuit is connected with the input end of the starting circuit. The input end of the control circuit is connected with the output ends of the starting circuit, the fly-back switch circuit and the feedback circuit while the output end of the control circuit is connected with the input end of the fly-back switch circuit. Compared with a conventional power supply circuit, the fly-back switch power supply circuit has the advantages of fewer peripheral components, low cost and extremely low standby power consumption.

Description

Flyback switching power supply circuit

The present invention relates to the field of circuits, and more particularly to a novel low-cost flyback switching power supply circuit. Large starting resistors enable zero current start-up and low current operation, reduce system standby power consumption, meet the standby power consumption of five-star chargers of 30mW or lower, and the latest ENERGY STAR standard requirements .

Global energy is becoming increasingly tense, and energy conservation and emission reduction and green energy are the trend of the times. Relevant energy efficiency standards are becoming more and more strict. The new six-level energy efficiency has put forward 100mW standby requirements. Samsung, LG, Nokia and other big-name mobile phone manufacturers have jointly introduced a stricter standby grading system. The standby power consumption of the charger is less than 30mW, which is set to five stars. Level charger. Therefore, how to achieve ultra-low standby power consumption with a low-cost solution has become a competitive advantage for power management IC manufacturers.

In view of the above problems, this creation proposes a low-cost flyback switching power supply circuit.

A low-cost flyback switching power supply circuit according to an embodiment of the present invention includes: an AC rectifying circuit, the input end of the AC rectifying circuit is connected to an AC power source; an electromagnetic interference filtering circuit, the input of the electromagnetic interference filtering circuit The end is connected to the output end of the AC rectification circuit; a start circuit, the input end of the start circuit is connected to the output end of the electromagnetic interference filter circuit; a flyback switch circuit, the input end of the flyback switch circuit and the start An output end of the circuit is connected, an output end of the flyback switch circuit is connected to an input end of the start circuit; an output rectification filter circuit, an input end of the output rectification filter circuit is connected to an output end of the flyback switch circuit, An output end of the output rectification filter circuit is connected to a load; a control circuit, an input end of the control circuit is connected to an output end of the start circuit, an output end of the flyback switch circuit, and an output end of the feedback circuit, An output of the control circuit is coupled to an input of the flyback switch circuit, wherein the control circuit includes at least one pulse width a modulation control switch chip, the pulse width modulation control switch chip comprises eight pins; and a feedback circuit, the input end of the feedback circuit is connected with the output end of the flyback switch circuit, and the output end of the feedback circuit is The inputs of the control circuit are connected.

The low-cost flyback switching power supply circuit according to the present invention overcomes the current technical bottleneck, and has fewer peripheral components, lower cost, and extremely low standby power consumption than the existing power supply circuit.

Features and exemplary embodiments of various aspects of the present work are described in detail below. The following description covers many specific details to provide a thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely provided to provide a clearer understanding of the present invention by the example of the present invention. The present invention is in no way limited to any specific configuration as set forth below, but without departing from the spirit of the present invention, any modification, substitution, or modification of the related elements or components.

This creation proposes a low-cost flyback switching power supply circuit. 1 is a block diagram showing a low cost flyback switching power supply circuit in accordance with the presently-created embodiment. As shown in FIG. 1 , the flyback switching power supply circuit includes an AC rectification circuit A, an electromagnetic interference filter circuit B, a startup circuit C, a flyback switch circuit D, an output rectification and filtering circuit E, and a control circuit F and a feedback circuit G. And the flyback switching circuit D further includes an absorption circuit H.

Wherein, the input end of the AC rectification circuit A is connected to the AC power source, the output end is connected to the input end of the electromagnetic interference filter circuit B; the input end of the electromagnetic interference filter circuit B is connected to the output end of the AC rectification circuit A, and the output end Connected to the input end of the starting circuit C; the input end of the starting circuit C is connected to the output end of the electromagnetic interference circuit B, and the output end is connected to the input end of the flyback switching circuit D and the input end of the control circuit F; The input end of the switch circuit D is connected to the output end of the start circuit C and the output end of the control circuit F, and the output end is connected with the input end of the feedback circuit G, the input end of the output rectification filter circuit E, and the input end of the control circuit F. Connection; the input end of the output rectification filter circuit E is connected to the output end of the flyback switch circuit D, and the output end is connected to the load; the input end of the control circuit F and the output end of the start circuit C, and the output of the flyback switch circuit D The output end of the terminal and the feedback circuit G are connected, the output end is connected to the input end of the flyback switch circuit D; the input end of the feedback circuit G is connected to the output end of the flyback switch circuit D. , The input terminal and the output terminal F is connected to the control circuit.

Fig. 2 is a circuit diagram showing a flyback switching power supply circuit according to an embodiment of the present invention. As shown in FIG. 2, the flyback switching power supply circuit according to an embodiment of the present invention includes an AC rectification circuit 1 and an Electromagnetic Interference (EMI) filter circuit 2. The startup circuit 3, the absorption circuit 4, the flyback switch circuit 5, the output rectification filter circuit 6, the feedback circuit 7, and the control circuit 8.

In the embodiment shown in FIG. 2, the AC rectifying circuit 1 includes a fuse resistor RF (FUSE) and rectifying diodes D1 to 4, and the main function is to rectify the AC voltage. The number of rectifying diodes may be at least one and may be at most eight. The fuse can also be replaced by a fuse resistor, wirewound resistor or inductor.

In the embodiment shown in FIG. 2, the EMI filter circuit 2 includes an inductor L1, an inductor L2, a high voltage electrolytic capacitor C1, a high voltage electrolytic capacitor C2, and an electrostatic discharge (ESD) resistor R7. The main function is to suppress EMI and After rectification filtering. Depending on the application, an EMI filter circuit can use one inductor, two inductors, or only one common mode inductor; only one high voltage electrolytic capacitor can be used; and in some cases, the ESD resistor R7 can be omitted. The 2a icon shows a variety of connections for the EMI filter circuit, where R7 is an ESD resistor, which can be connected in series or in parallel to achieve the desired resistance value, or can be eliminated.

In the embodiment shown in FIG. 2, the main function of the starting circuit 3 is to charge the starting capacitor C3 through the starting resistor R1 and the starting resistor R2, and charge the starting capacitor C4 via the pin PIN-A of the control circuit 8 to achieve startup. The purpose of the control circuit 8. The startup resistor can select a relatively large resistance value to achieve a "zero" current start, reduce the power loss of the startup circuit, and reduce the system standby power consumption.

In the embodiment shown in Fig. 2, the absorbing circuit 4 can be varied according to different system requirements. Further, the absorbing circuit can also be completely eliminated according to different market requirements, thereby further reducing the cost. Figure 2b shows a variety of connections for the snubber circuit.

In the embodiment shown in FIG. 2, the flyback switching circuit 5 includes a flyback transformer T1 and a current detecting resistor Rs. The main function is to convert the AC rectified high voltage DC voltage into a lower secondary AC through a flyback transformer. Voltage. The current detecting resistor Rs can achieve the required resistance value in series or in parallel.

In the embodiment shown in FIG. 2, the output rectification filter circuit 6 includes two main portions of the output rectifying diode D4 and the filter capacitor Co. For different output ripple requirements, the output rectification filter circuit 6 can increase the π-type filter circuit or the common mode filter circuit to improve the filtering effect. Figure 2c shows two connections for two enhanced output rectification and filtering circuits to achieve different ripple requirements.

In the embodiment shown in FIG. 2, the feedback circuit 7 includes a sampling resistor R5 and a sampling power. Resistor R6, the main function is to use the sampling resistor R5 and the sampling resistor R6 to send the secondary AC voltage (AC voltage on the feedback winding) proportionally induced by the primary power supply winding of the transformer to the control circuit 8. In principle, there are no optocouplers and secondary reference regulators, which significantly reduces costs. The sampling resistors can achieve the required resistance values in series or in parallel.

In the embodiment shown in FIG. 2, the main device of the control circuit 8 is a Pulse Width Modulation (PWM) control switch chip IC1 and necessary peripheral auxiliary components, wherein the internal integration gold in the control circuit 8 Oxygen Half Field Effect Transistor (MOSFET). For example, an OB2552 or similar function control switch chip, the PWM control switch chip IC1 comprises a total of eight pins PIN-A to PIN-H, respectively: a power supply pin PIN-A for supplying the working voltage to the chip, Connected to the output end of the start-up circuit 3; the drive pin PIN-B is connected to the output terminal of the start-up circuit 3 for the operation state of the MOSFET integrated in the PWM control switch chip IC1, the PWM control switch chip IC1 Directly connected to the gate of the internally integrated MOSFET; feedback signal pin PIN-C for detecting the output voltage of the flyback switching power supply circuit, connected to the output of the feedback circuit 7; current detecting pin PIN-D, It is used for detecting the primary current of the flyback switching circuit 5, and controlling the off of the internal integrated MOSFET according to the detected current; the MOSFET drain pin PIN-E/F is connected to the output terminal of the flyback switching circuit 5 And the grounding pin PIN-G/H for grounding, wherein the PIN pin sequence is not limited to the above sequence.

The present invention has been described above with reference to the specific embodiments of the present invention, but it is understood that various modifications, combinations and changes may be made to the specific embodiments without departing from the scope of the appended claims. Limit the spirit and scope of this creation. In addition, any signal arrows in the figures should be considered as illustrative only and not limiting, unless specifically indicated otherwise. Combinations of elements or steps are also considered to have been described when the term is foreseen to be unclear.

1‧‧‧AC rectifier circuit

2‧‧‧Electromagnetic interference filter circuit

3‧‧‧Starting circuit

4‧‧‧Absorption circuit

5‧‧‧ flyback switching circuit

6‧‧‧Output rectification filter circuit

7‧‧‧Feedback circuit

8‧‧‧Control circuit

A‧‧‧AC rectifier circuit

B‧‧‧Electromagnetic interference filter circuit

C‧‧‧Starting circuit

D‧‧‧ flyback switch circuit

E‧‧‧Output rectification filter circuit

F‧‧‧Control circuit

G‧‧‧ feedback circuit

H‧‧‧ absorption circuit

C1, C2‧‧‧ high voltage electrolytic capacitor

C3‧‧‧Starting Capacitor

C4‧‧‧Starting Capacitor

Co‧‧‧Filter Capacitor

D1~4‧‧‧Rected Diode

D4‧‧‧ Output Rectifier Diode

IC1‧‧‧ Pulse width modulation control switch chip

L1, L2‧‧‧ inductance

PIN-A‧‧‧ power supply pin

PIN-B‧‧‧ drive pin

PIN-C‧‧‧ feedback signal pin

PIN-D‧‧‧ current detection pin

PIN-E/F‧‧‧MOSFET 接 pin

PIN-G/H‧‧‧ grounding pin

R1, R2‧‧‧ start resistor

R5, R6‧‧‧ sampling resistor

R7‧‧‧Electrostatic Discharge Resistor

RF‧‧‧Fuse resistance

Rs‧‧‧ current sense resistor

T1‧‧‧ flyback transformer

The present invention can be better understood from the following description of the specific embodiments of the present invention with reference to the accompanying drawings, wherein: FIG. 1 is a block diagram showing a low-cost flyback switching power supply circuit according to the present embodiment; The figure shows the power of a low cost flyback switching power supply circuit according to the present creative embodiment. Road diagram; Figure 2a shows the various connections of the EMI filter circuit; Figure 2b shows the various connections of the snubber circuit; and Figure 2c shows the two connections of the two reinforced output rectifier filter circuits .

A‧‧‧AC rectifier circuit

B‧‧‧Electromagnetic interference filter circuit

C‧‧‧Starting circuit

D‧‧‧ flyback switch circuit

E‧‧‧Output rectification filter circuit

F‧‧‧Control circuit

G‧‧‧ feedback circuit

H‧‧‧ absorption circuit

Claims (9)

A flyback switching power supply circuit comprising: an AC rectification circuit, an input end of the AC rectification circuit is connected to an AC power supply; an electromagnetic interference filter circuit, an input end of the electromagnetic interference filter circuit and the AC rectification circuit An output terminal is connected; a start circuit, an input end of the start circuit is connected to an output end of the electromagnetic interference filter circuit; a flyback switch circuit, an input end of the flyback switch circuit and the start circuit An output end of the flyback switch circuit is connected to the input end of the start circuit; an output rectification filter circuit, an input end of the output rectification filter circuit and the flyback switch circuit The output end is connected, an output end of the output rectification filter circuit is connected to a load; a control circuit, an input end of the control circuit and the output end of the start circuit, the output end of the flyback switch circuit and An output end of a feedback circuit is connected, an output end of the control circuit is connected to the input end of the flyback switch circuit, wherein the control The circuit includes at least a pulse width modulation control switch chip, the pulse width modulation control switch chip includes eight pins, and a feedback circuit, an input end of the feedback circuit and the output end of the flyback switch circuit Connected, an output of the feedback circuit is coupled to the input of the control circuit. The flyback switching power supply circuit of claim 1, wherein the flyback switching circuit further comprises an absorbing circuit spanning two of a primary winding of a flyback transformer in the flyback switching circuit end. The flyback switching power supply circuit of claim 1, wherein the AC rectifying circuit comprises a fuse resistor and at least one rectifying diode. The flyback switching power supply circuit of claim 1, wherein the electromagnetic interference filter circuit comprises at least one inductor, at least one high voltage electrolytic capacitor, and an electrostatic discharge resistor to suppress electromagnetic interference and rectification filtering. The flyback switching power supply circuit of claim 1, wherein the starting circuit charges a capacitor through at least one starting resistor, and connects a driving pin of the pulse width modulation control switch chip, the driving The pin is connected to a gate of a MOS field-effect transistor integrated as a switching element inside the control circuit. The flyback switching power supply circuit of claim 1, wherein the starting circuit charges a power supply capacitor before starting by a starting resistor. The flyback switching power supply circuit of claim 1, wherein the flyback switching circuit comprises a flyback transformer and a current detecting resistor for passing an AC rectified high voltage DC voltage through the flyback transformer Converted to a lower secondary AC voltage. The flyback switching power supply circuit of claim 1, wherein the output rectifying and filtering circuit comprises an output rectifying diode and a filtering capacitor. The flyback switching power supply circuit of claim 1, wherein the feedback circuit includes a plurality of sampling resistors for using the sampling resistors to proportionally induce a primary power supply winding through a transformer. The AC voltage is sent to the control circuit.