CN215186493U

CN215186493U - Two-way isolated output AC/DC power supply

Info

Publication number: CN215186493U
Application number: CN202120692924.8U
Authority: CN
Inventors: 林利弘; 尹亚娟
Original assignee: Shaanxi Henghai Tiandi Intelligent Technology Co ltd
Current assignee: Shaanxi Henghai Tiandi Intelligent Technology Co ltd
Priority date: 2021-04-06
Filing date: 2021-04-06
Publication date: 2021-12-14
Anticipated expiration: 2031-04-06

Abstract

The utility model provides an output AC DC power is kept apart to two tunnel, include: the primary side regulation flyback transformer comprises a primary side winding, a secondary winding and an auxiliary winding, wherein the auxiliary winding and the primary side winding are positioned on the same side of the primary side regulation flyback transformer, and the auxiliary winding and the primary side winding are grounded. The utility model discloses a technique of former limit feedback control realizes feedback function and output regulatory function, because no longer follow the output (being secondary side direct sampling), but calculates the condition of secondary side coil through the auxiliary coil sampling of primary side, further calculates the condition of output, so cancelled many auxiliary devices such as expensive opto-coupler and TL431, has not only reduced the device cost and has also reduced PCB's occupation space.

Description

Two-way isolated output AC/DC power supply

Technical Field

The utility model relates to a power technical field especially relates to an output AC DC power is kept apart to two tunnel.

Background

An AC/DC Power Supply, also called a Switch Mode Power Supply (SMPS), is a Power Supply that maintains a stable output voltage by controlling the on/off time ratio of a switching tube using modern Power electronics technology. The main components are as follows: AC input, EMI filtering, rectification filtering, inversion, output, feedback and the like. The feedback part is used for sampling from the output end to obtain an error signal, then transmitting the error signal back to a PWM controller of the primary input end IC, and realizing high-precision voltage stabilization output by adjusting the PWM duty ratio. In the conventional technical scheme, the optical coupler and multiple devices such as the TL431 are combined to realize the detection and feedback functions of the output end parameters. The prior art has the following defects:

(1) in the occasion that the PCB installation space is limited, due to the fact that devices are numerous, such as an optical coupler and a TL431 device, a plurality of peripheral auxiliary devices and the like are used, the devices are difficult to arrange and place;

(2) the design of two-way isolation output is difficult to realize in a limited space, because the two-way isolation output increases a plurality of devices on the basis of single-way output;

(3) the device is many, and is with high costs.

(4) The service life of the optical coupler used by feedback can also become the bottleneck of the power supply of the original scheme.

SUMMERY OF THE UTILITY MODEL

The utility model aims at: the circuit is simplified, the cost is reduced, the circuit size is reduced, and the convenience of the layout of the switching power supply is further increased.

Specifically, the utility model provides an output AC/DC power is kept apart to two tunnel, include:

the primary side regulation flyback transformer comprises a primary side winding, a secondary winding and an auxiliary winding, wherein the auxiliary winding and the primary side winding are positioned on the same side of the primary side regulation flyback transformer, and the auxiliary winding and the primary side winding are grounded.

Furthermore, the AC/DC power supply further comprises an input rectification filter circuit, a clamping buffer circuit, a constant voltage sampling circuit and a control circuit; the first side of the input rectifying and filtering circuit is connected with the first side of the clamping buffer circuit, the second side of the input rectifying and filtering circuit is connected with the first side of the control circuit, the second side of the clamping buffer circuit is connected with the primary winding, and the third side of the clamping buffer circuit is connected with the second side of the control circuit; the auxiliary winding is connected with the first side of the constant voltage sampling circuit, and the second side of the constant voltage sampling circuit is connected with the third side of the control circuit.

Further, the AC/DC power supply further comprises an output circuit and a low dropout regulator; the secondary winding is connected with one side of the output circuit, and the other side of the output circuit is connected with the low dropout regulator.

Further, the control circuit includes an IC chip.

Further, the input rectifying and filtering circuit comprises a rectifying diode bridge, a first capacitor, a second capacitor, an inductor and a resistor; the first capacitor and the second capacitor are connected between the output ends of the rectifier diode bridge in a bridge-connected mode, and the inductor and the resistor are connected between the anodes of the first capacitor and the second capacitor in parallel.

Further, the clamp snubber circuit includes: the circuit comprises a first resistor, a capacitor, a diode and a second resistor, wherein the first resistor and the capacitor are connected in parallel and then connected with the cathode of the diode, and the anode of the diode is connected with the second resistor.

Furthermore, the secondary winding, the output circuit and the low dropout regulator are all one, or the secondary winding, the output circuit and the low dropout regulator are all two.

Further, the auxiliary winding is connected with the drain terminal of the IC chip.

Further, the output circuit comprises a diode, a resistor and a capacitor, wherein the resistor and the capacitor are connected in series and then are bridged at two ends of the diode.

Further, the constant voltage sampling circuit comprises an upper resistor and a lower resistor which are connected in series, and a connecting line between the upper resistor and the lower resistor is connected with the FB port of the control circuit.

The utility model has the advantages that:

(1) an optical coupler and all secondary Constant Voltage (CV)/Constant Current (CC) control circuits are omitted;

(2) the compensation circuit in all control loops is omitted;

(3) a dummy load at the output end is saved;

(4) by using an LDO (low dropout regulator) on the secondary side, the output voltage is a stable value no matter no load/light load or full load;

(5) the number and the cost of devices are reduced, the PCB layout is convenient, and the size of the scheme is reduced.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

fig. 1 shows a two-way isolated output AC/DC power circuit architecture diagram based on PSR technology according to an embodiment of the present invention.

Fig. 2 shows a schematic diagram of a two-way isolated output AC/DC power circuit based on PSR technology according to an embodiment of the present invention.

Fig. 3 shows a schematic diagram of an AC input rectifying and filtering circuit according to an embodiment of the present invention.

Fig. 4 shows a schematic diagram of an RCD clamp snubber circuit according to an embodiment of the present invention.

Fig. 5 shows a schematic diagram of a start-up waveform according to an embodiment of the present invention.

Fig. 6 shows a key waveform diagram of a primary side regulation flyback transformer according to an embodiment of the present invention.

Fig. 7 shows a schematic diagram of an auxiliary winding voltage waveform according to an embodiment of the invention.

Fig. 8 shows a schematic diagram of a constant voltage sampling circuit according to an embodiment of the present invention.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

The utility model discloses a Primary Side feedback Regulation or the technique of the Regulation of the Primary Side realize feedback function and output regulatory function promptly in Primary Side feedback Regulation (PSR), because no longer follow the output (secondary Side directly samples promptly), but calculate the condition of secondary Side coil through the auxiliary coil sampling of Primary Side, further calculate the condition of output, so cancelled a lot of auxiliary devices such as expensive opto-coupler and TL431, not only reduced the device cost and also reduced PCB's occupation space.

As shown in fig. 1, the utility model discloses a two way isolation output AC/DC power based on PSR technique, include: the primary side regulation flyback transformer comprises a primary side winding, a secondary winding and an auxiliary winding, wherein the auxiliary winding and the primary side winding are positioned on the same side of the primary side regulation flyback transformer, and the auxiliary winding and the primary side winding are grounded.

The AC/DC power supply further comprises an input rectification filter circuit, a clamping buffer circuit, a constant voltage sampling circuit, a control circuit, an output circuit and a low dropout regulator; the first side of the input rectifying and filtering circuit is connected with the first side of the clamping buffer circuit, the second side of the input rectifying and filtering circuit is connected with the first side of the control circuit, the second side of the clamping buffer circuit is connected with the primary winding, and the third side of the clamping buffer circuit is connected with the second side of the control circuit; the auxiliary winding is connected with the first side of the constant voltage sampling circuit, and the second side of the constant voltage sampling circuit is connected with the third side of the control circuit. The secondary winding is connected with one side of the output circuit, and the other side of the output circuit is connected with a low dropout regulator (LDO).

Fig. 2 shows a schematic diagram of a two-way isolated output AC/DC power circuit based on PSR technology according to an embodiment of the present invention. The figure marks each component element of the AC/DC power supply and the parameters, pins, models, etc. thereof. Wherein the control circuit is realized by an IC chip. Other details may be continued with reference to the following exploded description.

It should be further emphasized that, although fig. 2 shows two secondary windings and two corresponding output circuits and two low dropout regulators, it can be understood by those skilled in the art that the present invention can also be implemented with only 1 secondary winding and one corresponding output circuit and one low dropout regulator.

Fig. 3 shows a schematic diagram of an AC input rectifying and filtering circuit according to an embodiment of the present invention, which includes bridge rectifier diodes, C1 and C2 are polar capacitors, inductors L and resistors R. Wherein the inductor L and the resistor R are connected in parallel. The input rectifying filter circuit converts the input alternating current into direct current.

Fig. 4 shows a schematic diagram of an RCD clamp snubber circuit according to an embodiment of the present invention. The RCD clamping buffer circuit comprises: resistance R_SNCapacitor C_SNDiode D_SNWherein the resistance R_SNAnd a capacitor CS_SNAfter being connected in parallel, the diodes D are connected in series_SNAnd a resistance R.

The core circuit of the present invention is as follows, as shown in fig. 2:

1. an auxiliary winding Na is adopted on the primary side, the auxiliary winding Na and a primary winding Np are grounded, and the auxiliary winding Na is isolated from two secondary windings Ns1 and Ns2, and can simultaneously realize two functions:

the method comprises the following steps: the transformer and the primary and secondary windings form a flyback structure to supply power to the control circuit IC, and a voltage-limiting and rectifying diode D6 is required to be added because the flyback structure cannot realize constant voltage;

secondly, the step of: the auxiliary winding divides voltage through resistors Rup and Rdown, the voltage conditions of a primary side and a secondary side are reflected on a VFB point (voltage of a pin tube in an IC chip), at the moment, the auxiliary winding Na and the primary side winding Np form a transformer, and the auxiliary winding Na and two secondary windings Ns1 and Ns2 also form two transformers respectively;

2. the final voltage stabilization and application are realized by adopting a low dropout regulator (LDO) at an output end (secondary side), and the LDO also has the function of a dummy load (the current and the voltage can be stabilized no matter the LDO is fully loaded, unloaded or lightly loaded).

The above section 1 is explained in detail as follows:

when the commercial power AC220V is applied to the switching power supply, the control IC draws current through the chip pin Drain by using its internal high-voltage start current source circuit, thereby self-powering the chip. When the voltage of the chip V CC reaches V CC _ ON, a high-voltage current source in the chip is closed, and meanwhile, a pulse signal GATE (if an MOSFET is integrated in the chip, the signal is an internal signal) for driving a MOSFET switch is output, the MOSFET and a primary winding (namely a primary side) Np of a high-frequency transformer form a conducting loop, current flows through the primary winding Np for storing energy, the primary winding Np and an auxiliary winding Na form a transformer, voltage is generated ON the auxiliary winding Na at the moment, and the voltage can supply power to the IC through a voltage-limiting and rectifying diode D6, so that the function in the item I is completed. When the voltage of the chip VCC is reduced to VCC _ OFF, the pulse signal GATE for driving the MOSFET switch is closed and disappears, and the internal high-voltage current source is restarted. Related figures as shown in fig. 5 below, a start-up waveform diagram according to an embodiment of the present invention is shown.

Fig. 6 shows a key waveform diagram of a primary side regulation flyback transformer according to an embodiment of the present invention. The meanings of the letters in the figures are as follows:

ip: the primary side (primary winding) current, which is also the current flowing through the drain to source of the MOSFET;

ipk: primary side (primary winding) peak current;

is: secondary side (secondary winding) current, which is also the current flowing through the secondary side diode;

np: the number of primary winding turns;

ns: the number of turns of the secondary winding;

na: the number of turns of the auxiliary winding;

ia.avg: an average current flowing through the secondary side diode;

io: a secondary output current;

v F: a secondary side diode forward voltage drop;

v O: a secondary side output voltage;

tp _ on: primary side MOSFET switch on-time;

ts _ on: the secondary side diode conduction time;

ts: one switching duty cycle.

During the conduction of the diode D7 or D9 at the secondary (i.e. secondary) side, the sum of the output voltage and the forward voltage drop of the diode D7 or D9 is reflected on the auxiliary winding Na of the transformer at a value of

As the current decreases, the forward voltage drop of the diode D7 or D9 also decreases, and the auxiliary winding voltage optimally reflects the output voltage at the end of the diode D7 or D9 current drop to zero, i.e., the diode D7 or D9 conduction time (which is also the auxiliary winding degaussing time). Therefore, the output voltage information can be obtained by sampling the auxiliary winding Na voltage at the time when the diode D7 or D9 is turned on and off.

Fig. 7 is a graph of the auxiliary winding voltage waveform of fig. 6, and the present invention can be further illustrated. In fig. 7, Va is the voltage on the auxiliary winding,

the output circuit of one secondary winding comprises a diode D7, a resistor R21 and a capacitor C8, wherein the resistor and the capacitor are connected in series and then are connected across the two ends of the diode. The other secondary winding is similar and will not be described in detail.

As shown in fig. 8 below, the constant voltage sampling circuit of the present invention includes resistors Rup and Rdown connected in series, and a connection line between Rup and Rdown connects an FB (feedback) port of a control IC. And the FB pin of the IC controller samples the voltage after the auxiliary winding is demagnetized for 3.5us through the voltage division of the resistors Rup and Rdown and keeps the voltage till the next sampling period. The sampling voltage is compared and amplified with the internal 4.0V reference voltage, and the operating frequency of the chip is adjusted through a PFM (pulse frequency modulation mode) control circuit.

Note that: the above-mentioned 3.5us time parameter and 4.0V reference voltage parameter may be different for control ICs of different manufacturers, for example, some manufacturer parameters are: 1.4us, 2.5 us; 3.8V, 1.2V, etc., with specific reference to the respective manufacturer's data manual.

Namely:

in fig. 7, at the point s of the circle (the turn-on and turn-off time of the secondary-side diode), that is, the demagnetization point is sampled, the secondary-side diode V F is 0,

at this time

In the formula, V FB is the FB terminal sampling point voltage, and V FB of an IC of a certain manufacturer is 4.0V. In the design, when Ns, Na, Rup and Rdown are determined, V O values of constant voltage output can be obtained.

The specific value of Rup can be obtained from the equation for the compensation voltage of the cable under full load condition of the converter, which is available in IC data manuals of different manufacturers. In case of Rup determination, the Rdown value can be found by the equation three. These two parameters must be chosen with a resistance with an accuracy level of 1%.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention should be covered by the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. A two-way isolated output AC/DC power supply, comprising:

2. The two-way isolated output AC/DC power supply of claim 1,

the AC/DC power supply further comprises an input rectification filter circuit, a clamping buffer circuit, a constant voltage sampling circuit and a control circuit; the first side of the input rectifying and filtering circuit is connected with the first side of the clamping buffer circuit, the second side of the input rectifying and filtering circuit is connected with the first side of the control circuit, the second side of the clamping buffer circuit is connected with the primary winding, and the third side of the clamping buffer circuit is connected with the second side of the control circuit; the auxiliary winding is connected with the first side of the constant voltage sampling circuit, and the second side of the constant voltage sampling circuit is connected with the third side of the control circuit.

3. The two-way isolated output AC/DC power supply of claim 1,

the AC/DC power supply further comprises an output circuit and a low dropout regulator; the secondary winding is connected with one side of the output circuit, and the other side of the output circuit is connected with the low dropout regulator.

4. The two-way isolated output AC/DC power supply of claim 2,

the control circuit includes an IC chip.

5. The two-way isolated output AC/DC power supply of claim 2,

the input rectifying and filtering circuit comprises a rectifying diode bridge, a first capacitor, a second capacitor, an inductor and a resistor; the first capacitor and the second capacitor are connected between the output ends of the rectifier diode bridge in a bridge-connected mode, and the inductor and the resistor are connected between the anodes of the first capacitor and the second capacitor in parallel.

6. The two-way isolated output AC/DC power supply of claim 2,

the clamp snubber circuit includes: the circuit comprises a first resistor, a capacitor, a diode and a second resistor, wherein the first resistor and the capacitor are connected in parallel and then connected with the cathode of the diode, and the anode of the diode is connected with the second resistor.

7. A two-way isolated output AC/DC power supply according to claim 3,

the secondary winding, the output circuit and the low dropout regulator are all one, or the secondary winding, the output circuit and the low dropout regulator are all two.

8. The two-way isolated output AC/DC power supply of claim 4,

the auxiliary winding is connected with the drain terminal of the IC chip.

9. A two-way isolated output AC/DC power supply according to claim 3,

the output circuit comprises a diode, a resistor and a capacitor, wherein the resistor and the capacitor are connected in series and then bridged at two ends of the diode.

10. The two-way isolated output AC/DC power supply of claim 2,

the constant voltage sampling circuit comprises an upper resistor and a lower resistor which are connected in series, and a connecting line between the upper resistor and the lower resistor is connected with an FB port of the control circuit.