High-precision multi-output flyback switching power supply circuit and method

Abstract

The present application relates to a high-precision multi-output flyback switching power supply circuit and method, including at least two power output circuits connected to the secondary coil of a power chip and a control chip for controlling the at least two power output circuits, the at least two power output circuits including a first power output circuit and a second power output circuit connected in parallel with the first power output circuit, the second power output circuit including a switch for turning it on, the control chip being connected to the switch; a reference voltage value is preset in the control chip, and when the control chip detects that the output voltage value of the second power output circuit is less than the reference voltage value, the control chip controls the switch to close so that the second power output circuit is turned on. The present application is provided with a control chip for controlling the first power output circuit and the second power output circuit, and actively controls the multi-output voltage to achieve the effect of good load regulation and high output voltage accuracy.

Description

Technical Field

[0001] The invention relates to a high-precision multi-output flyback switching power supply circuit and method, belonging to the technical field of switching power supplies. Background Art

[0002] With the rapid development of power electronics technology, the relationship between power electronics and people's work and life is becoming increasingly close. Power electronics cannot do without reliable power supplies. The efficiency and output accuracy of power supplies have always been the two main performance indicators pursued by power supply researchers. Its power supply generally adopts a switching power supply. The switching power supply uses modern power electronics technology to control the time ratio of the switch tube to open and close, and maintain a stable output voltage. Among them, the flyback switching power supply is the simplest one in the switching power supply topology. The output transformer also acts as an energy storage inductor. The entire power supply is small in size and simple in structure. It can output multiple isolated voltages at the same time, so it has been widely used. However, although the demand for current multi-output switching power supplies has increased, their accuracy is relatively low and the load regulation rate is poor. Summary of the invention

[0003] The object of the present invention is to provide a high-precision multi-output flyback switching power supply circuit and method, which can actively control the multi-output voltage to achieve good load regulation and high output voltage accuracy.

[0004] To achieve the above-mentioned purpose, the present invention provides the following technical solutions: a high-precision multi-output flyback switching power supply circuit, comprising at least two power output circuits connected to the secondary coil of a power supply chip and a control chip for controlling the at least two power output circuits, the at least two power output circuits comprising a first power output circuit and a second power output circuit connected in parallel with the first power output circuit, the second power output circuit comprising a switch for turning it on, and the control chip is connected to the switch; the output voltage of the first power output circuit is transmitted to the primary auxiliary coil through the secondary coil mutual inductance to act on the power supply chip, a reference voltage value is preset in the control chip, and when the control chip detects that the output voltage value of the second power output circuit is less than the reference voltage value, the control chip controls the switch to close so that the second power output circuit is turned on.

[0005] Furthermore, the first power supply output circuit includes a first diode, a first capacitor and a first power supply output end connected to the first capacitor, the first end of the first diode is connected to the secondary coil, the second end of the first diode is connected to the first end of the first capacitor, and the second end of the first capacitor is grounded.

[0006] Furthermore, the second power supply output circuit also includes a second diode, a second capacitor and a second power supply output end connected to the second capacitor, the first end of the second diode is connected to the secondary coil and the first end of the first diode, the second end of the second diode is connected to the switch, the first end of the second capacitor is connected to the switch, and the second end of the second capacitor is grounded.

[0007] The present invention also provides a high-precision multi-output flyback switching power supply circuit, comprising at least two power output circuits connected to the secondary coil of a power chip, a control chip and a secondary feedback circuit for controlling the at least two power output circuits, the at least two power output circuits comprising a first power output circuit, and a second power output circuit connected in parallel with the first power output circuit, the second power output circuit comprising a switch for turning it on, and the control chip is connected to the switch; the output voltage of the first power output circuit is directly fed back to the power chip via the secondary feedback circuit, a reference voltage value is preset in the control chip, and when the control chip detects that the output voltage value of the second power output circuit is less than the reference voltage value, the control chip controls the switch to close so that the second power output circuit is turned on.

[0008] Furthermore, the secondary side feedback circuit includes a secondary side control chip and an optocoupler for feeding back the output voltage of the first power output circuit to the power chip, and the optocoupler is connected to the secondary side control chip; wherein the secondary side control chip is integrated with the control chip.

[0009] Furthermore, an output voltage value of the first power output circuit is greater than an output voltage value of the second power output circuit.

[0010] The present invention also provides a high-precision multi-output power supply method, using the high-precision multi-output flyback switching power supply circuit as described above, the method comprising:

[0011] The switch of the second power output circuit is turned off, and the second power output circuit is not conducting. At this time, the current of the first power output circuit is equal to the current of the secondary coil;

[0012] A reference voltage value is preset in the control chip. After the control chip detects that the second output voltage value of the second power supply output circuit is less than the reference voltage value, the control chip controls the switch to close so that the second power supply output circuit is turned on. At this time, the current of the second power supply output circuit is equal to the current of the secondary coil.

[0013] Furthermore, the method further comprises:

[0014] When the second power output circuit is turned on, the first power output circuit is turned off.

[0015] Furthermore, the method further comprises:

[0016] The output voltage value of the first power output circuit is greater than the output voltage value of the second power output circuit, and the first power output circuit has a minimum conduction time.

[0017] The beneficial effects of the present invention are: by providing a control chip for controlling the first power output circuit and the second power output circuit, multiple output voltages are adjusted in an active control manner, thereby achieving the effects of good load regulation and high output voltage accuracy;

[0018] By adopting a time division multiplexing working mode, at least two power supply output circuits are made independent of each other and do not interfere with each other, thereby improving the working efficiency of the power supply.

[0019] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The structure block diagram of the high-precision multi-output flyback switching power supply circuit of the present invention.

[0021] Figure 2 It is a schematic diagram of a high-precision multi-output flyback switching power supply circuit of the present invention.

[0022] Figure 3 for Figure 2 Schematic diagram of the waveform.

[0023] Figure 4 The diagram is a schematic diagram of a high-precision multi-output flyback switching power supply circuit including a secondary-side feedback circuit according to the present invention.

[0024] Figure 5 It is a flow chart of the high-precision multi-output power supply method of the present invention. DETAILED DESCRIPTION

[0025] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0026] See also Figure 1 and Figure 2In a preferred embodiment of the present invention, a high-precision multi-output flyback switching power supply circuit includes at least two power output circuits connected to the secondary coil 1 of the power chip and a control chip 2 for controlling the at least two power output circuits, and the secondary coil 1 is mutually inductive with the primary auxiliary coil. In this embodiment, the switching power supply circuit includes two power output circuits, namely a first power output circuit 3 and a second power output circuit 4 connected in parallel with the first power output circuit 3. Of course, in other embodiments, the number of the power output circuits may also be other, which is not specifically limited here and depends on the actual situation. Among them, the second power output circuit 4 includes a switch K1 for turning it on, the out pin of the control chip 2 is connected to the switch, and the out pin of the control chip 2 outputs the SK control signal. A reference voltage value Vx is preset in the control chip 2. When the control chip 2 detects that the output voltage value of the second power output circuit 4 is less than the reference voltage value Vx, the control chip 2 controls the switch to close so that the second power output circuit 4 is turned on.

[0027] It is worth noting that in this embodiment, the output voltage value of the first power output circuit 3 is greater than the output voltage value of the second power output circuit 4. The purpose of this setting is that when the second power output circuit 4 is turned on, the first power output circuit 3 is turned off, and they do not interfere with each other.

[0028] The first power output circuit 3 includes a first diode D1, a first capacitor C1 and a first power output end. The first end of the first diode D1 is connected to the secondary coil 1, the second end of the first diode D1 is connected to the first end of the first capacitor C1, the second end of the first capacitor C1 is grounded, and the voltage on the first capacitor C1 is the first power output end voltage VOUT1.

[0029] The second power output circuit 4 also includes a second diode D2, a second capacitor C2 and a second power output end. The first end of the second diode D2 is connected to the secondary coil 1 and the first end of the first diode D1. The second end of the second diode D2 is connected to the switch K1 and the OUT pin of the control chip 2. The first end of the second capacitor C2 is connected to the other end of the switch K1 and the IN pin of the control chip 2. The second end of the second capacitor C2 is grounded. The voltage on the second capacitor C2 is the voltage VOUT2 of the second power output end.

[0030] After the conduction switch of the primary side coil is turned off, current Is starts to flow through the secondary side coil 1. Since the switch K1 is not closed, Is1 = Is, and only the first power output circuit 3 has current, and the first capacitor C1 starts to charge. When the control chip 2 detects that the voltage at the second power output terminal is lower than a certain reference voltage, it will control the switch K1 to close. At the same time, the voltage at the first power output terminal is mutually induced to the primary side auxiliary coil through the secondary side coil 1 and acts on the power chip. After the switch K1 is closed, since VOUT2 < VOUT1, the first diode is difficult to conduct, so Is2 = Is, and only the second power output circuit 4 has current, and the second capacitor C2 starts to charge until the current drops to 0.

[0031] In the above control process, the voltage at the first power output terminal is mutually induced to the primary side auxiliary coil through the secondary side coil 1 and acts on the power chip, which is the primary side feedback method. When the power chip detects that the output voltage at the first power output terminal is too low, it will increase the peak current flowing through the secondary side coil 1; if it detects that the output voltage at the first power output terminal is too high, it will decrease the peak current flowing through the secondary side coil 1, so as to achieve precise control of the multi-output power supply voltage.

[0032] The waveform schematic diagram of the high-precision multi-output flyback switching power supply circuit of the present invention is as Figure 3 shown. From the periods of T1 and T2, it can be seen that after the secondary side coil 1 is turned on, current Is starts to flow. At first, the control signal SK of the switch K1 outputs a low level signal, the switch K1 is turned off, and the current Is1 = Is in the first power output circuit 3, and the output voltage VOUT1 at the first power output terminal rises. When the control chip 2 detects that the output voltage VOUT2 at the second power output terminal < Vx, the switch control signal SK outputs a high level signal, the switch K1 is closed, and the current Is2 = Is in the second power output circuit 4, and the output voltage VOUT2 at the second power output terminal rises. From the period of T3, it can be seen that when the output voltage VOUT2 at the second power output terminal is greater than Vx throughout the cycle, the current on the secondary side coil 1 always flows through the first power output circuit 3, and the output voltage VOUT1 at the first power output terminal rises. From the period of T4, it can be seen that VOUT1 has a minimum conduction time (tmin) to ensure that the first capacitor C1 stores electricity first. After a time delay of tmin, if it is detected that VOUT2 < Vx, the switch K1 is closed, and the current Is2 = Is in the second power output circuit 4, and the output voltage VOUT2 at the second power output terminal rises.

[0033] Please refer to Figure 4, which is different from the above-mentioned high-precision multi-output flyback switching power supply circuit, the high-precision multi-output flyback switching power supply circuit in this embodiment also includes a secondary feedback circuit, through which information is directly fed back to the power chip, which is a secondary feedback method. Specifically, it includes at least two power output circuits connected to the secondary coil 1 of the power chip, a control chip 2 for controlling the at least two power output circuits, and a secondary feedback circuit, wherein the at least two power output circuits include a first power output circuit 3, and a second power output circuit 4 connected in parallel with the first power output circuit 3, wherein the second power output circuit 4 includes a switch for turning it on, and the control chip 2 is connected to the switch; the output voltage of the first power output circuit 3 is fed back to the power chip via the secondary feedback circuit, and a reference voltage value is preset in the control chip 2. When the control chip detects that the output voltage value of the second power output circuit 4 is less than the reference voltage value, the control chip 2 controls the switch to close so that the second power output circuit is turned on.

[0034] The secondary feedback circuit includes a secondary control chip and an optocoupler for feeding back the output voltage of the first power output circuit 3 to the power chip. The secondary feedback circuit is integrated with the control chip 2 or is independently configured separately. In the present embodiment, the secondary feedback circuit is integrated with the control chip 2, that is, the secondary control chip is integrated with the control chip 2, and the secondary control chip is TL431. Of course, in other embodiments, the secondary control chip can also be other, depending on the actual situation, and is not specifically limited here. The optocoupler is connected to the OUT1 pin of the control chip 2, the second power output terminal is connected to the second input terminal IN2 of the control chip 2, and the second output terminal of the control chip 2 is connected to the control terminal of the first switch K1.

[0035] See also Figure 5 The present invention also provides a high-precision multi-output power supply method, using the high-precision multi-output flyback switching power supply circuit as described above, the method comprising:

[0036] The switch K1 of the second power output circuit 4 is disconnected, and the second power output circuit 4 is not conducting. At this time, the current of the first power output circuit 3 is equal to the current of the secondary coil 1. The first output voltage value of the first power output circuit 3 is fed back to the power chip via the secondary coil 1 or the secondary feedback circuit. The power chip outputs a pulse width modulation signal according to the first output voltage value.

[0037] A reference voltage value is preset in the control chip 2. After the control chip 2 detects that the output voltage value of the second power supply output circuit 4 is less than the reference voltage value, the control chip 2 controls the switch to close so that the second power supply output circuit 4 is turned on. At this time, the current of the second power supply output circuit 4 is equal to the current of the secondary coil 1.

[0038] The method further comprises:

[0039] When the second power output circuit 4 is turned on, the first power output circuit 3 is turned off. The output voltage of the first power output circuit 3 is greater than the output voltage of the second power output circuit 4, and the first power output circuit 3 has a minimum on time to ensure that the first capacitor C1 stores electricity first.

[0040] In summary: by providing a control chip 2 for controlling the first power output circuit 3 and the second power output circuit 4, the multiple output voltages are adjusted in an active control manner, thereby achieving the effects of good load regulation and high output voltage accuracy;

[0041] By adopting a time division multiplexing working mode, at least two power output circuits are made independent of each other and do not interfere with each other, thereby improving the working efficiency of the power supply.

[0042] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0043] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A high-precision multi-output flyback switching power supply circuit, characterized in that: The invention comprises at least two power output circuits connected to the secondary coil of a power chip and a control chip for controlling the at least two power output circuits, wherein the at least two power output circuits comprise a first power output circuit and a second power output circuit connected in parallel with the first power output circuit, wherein the second power output circuit comprises a switch for turning it on, and the control chip is connected to the switch; the output voltage of the first power output circuit is transmitted to the primary auxiliary coil via the mutual inductance of the secondary coil to act on the power chip, a reference voltage value is preset in the control chip, and when the control chip detects that the output voltage value of the second power output circuit is less than the reference voltage value, the control chip controls the switch to close so that the second power output circuit is turned on; wherein the output voltage value of the first power output circuit is greater than the output voltage value of the second power output circuit, and when the second power output circuit is turned on, the first power output circuit is turned off; and the first power output circuit has a minimum turn-on time.

2. The high-precision multi-output flyback switching power supply circuit according to claim 1, characterized in that: The first power output circuit includes a first diode, a first capacitor and a first power output end connected to the first capacitor, the first end of the first diode is connected to the secondary coil, the second end of the first diode is connected to the first end of the first capacitor, and the second end of the first capacitor is grounded.

3. The high-precision multi-output flyback switching power supply circuit according to claim 1, characterized in that: The second power supply output circuit also includes a second diode, a second capacitor and a second power supply output end connected to the second capacitor, the first end of the second diode is connected to the secondary coil and the first end of the first diode, the second end of the second diode is connected to the switch, the first end of the second capacitor is connected to the switch, and the second end of the second capacitor is grounded.

4. A high-precision multi-output flyback switching power supply circuit, characterized in that: The invention comprises at least two power output circuits connected to the secondary coil of a power chip, a control chip and a secondary feedback circuit for controlling the at least two power output circuits, wherein the at least two power output circuits comprise a first power output circuit and a second power output circuit connected in parallel with the first power output circuit, wherein the second power output circuit comprises a switch for turning on the second power output circuit, and the control chip is connected to the switch; the output voltage of the first power output circuit is directly fed back to the power chip via the secondary feedback circuit, a reference voltage value is preset in the control chip, and when the control chip detects that the output voltage value of the second power output circuit is less than the reference voltage value, the control chip controls the switch to close so that the second power output circuit is turned on; wherein the output voltage value of the first power output circuit is greater than the output voltage value of the second power output circuit, and when the second power output circuit is turned on, the first power output circuit is turned off; and the first power output circuit has a minimum turn-on time.

5. The high-precision multi-output flyback switching power supply circuit according to claim 4, characterized in that: The secondary side feedback circuit includes a secondary side control chip and an optocoupler for feeding back the output voltage of the first power output circuit to the power chip, wherein the optocoupler is connected to the secondary side control chip; wherein the secondary side control chip is integrated with the control chip.

6. A high-precision multi-output power supply method, characterized in that: Using the high-precision multi-output flyback switching power supply circuit according to any one of claims 1 to 5, the method comprises: The switch of the second power output circuit is turned off, and the second power output circuit is not conducting. At this time, the current of the first power output circuit is equal to the current of the secondary coil; A reference voltage value is preset in the control chip. After the control chip detects that the second output voltage value of the second power output circuit is less than the reference voltage value, the control chip controls the switch to close so that the second power output circuit is turned on. At this time, the current of the second power output circuit is equal to the current of the secondary coil; When the second power output circuit is turned on, the first power output circuit is turned off; The output voltage value of the first power output circuit is greater than the output voltage value of the second power output circuit, and the first power output circuit has a minimum conduction time.

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