Accurate compensation open-loop power supply circuit and switching power supply

Abstract

The utility model discloses an accurately compensated open-loop power supply circuit and a switching power supply. The accurate compensation open-loop power supply circuit comprises a transformer, a self-adaptive load control circuit and at least one output circuit, the transformer comprises at least one secondary winding, and each secondary winding is connected with an actual load through a corresponding output circuit; the self-adaptive load control circuit comprises a threshold control unit, a driving filtering unit, a switching tube and a pseudo load. The first end of the threshold control unit is connected with an output circuit corresponding to the target secondary winding; the second end of the threshold control unit is connected with the first end of the driving filtering unit; the second end of the driving filtering unit is connected with the first end of the switching tube, and the third end of the driving filtering unit is connected with the output end cathode of the target secondary winding; the second end of the switching tube is connected with the output end positive electrode of the target secondary winding through a pseudo load, and the third end of the switching tube is connected with the output end negative electrode. The utility model can stabilize the output voltage and reduce the power loss of the circuit.

Description

TECHNICAL FIELD

[0001] The utility model belongs to power supply technical field especially relates to an open loop power supply circuit and switching power supply of accurate compensation. BACKGROUND

[0002] When the open loop power supply circuit works at light load or no load, it will enter intermittent working state, resulting in unstable output voltage, and further resulting in unreliable power supply. In related technologies, a dummy load is mainly added in the circuit to stabilize the output voltage through the dummy load. However, the addition of the dummy load increases the power loss of the circuit and reduces the efficiency of the circuit. SUMMARY

[0003] The utility model embodiment provides a kind of open loop power supply circuit and switching power supply of accurate compensation, to stabilize output voltage at dynamic load or no load, reduce the power loss of circuit.

[0004] The first aspect of the utility model embodiment provides an open loop power supply circuit with accurate compensation, comprising a transformer, an adaptive load control circuit and at least one output circuit. The transformer includes at least one secondary winding, and the number of secondary windings is the same as the number of output circuits. Each secondary winding is connected to an actual load through its corresponding output circuit. The adaptive load control circuit includes a threshold control unit, a drive filter unit, a switch tube, and a dummy load.

[0005] The first end of the threshold control unit is connected to the output circuit corresponding to the target secondary winding. The target secondary winding is one of the at least one secondary winding.

[0006] The second end of the threshold control unit is connected to the first end of the drive filter unit. The second end of the drive filter unit is connected to the first end of the switch tube, and the third end of the drive filter unit is connected to the output negative terminal of the target secondary winding.

[0007] The second end of the switch tube is connected to the output positive terminal of the target secondary winding through the dummy load, and the third end of the switch tube is connected to the output negative terminal.

[0008] In one embodiment, the switch tube includes an NPN triode, and the collector voltage of the NPN triode is greater than the base voltage, and the base voltage is greater than the emitter voltage.

[0009] In one embodiment, the drive filter unit includes a first resistor, a second resistor, and a first capacitor.

[0010] The first end of the first resistor serves as the first end of the drive filter unit.

[0011] The joint of the second end of the first resistor, the first end of the second resistor and the first end of the first capacitor is the second end of the driving filter unit;

[0012] The joint of the second end of the second resistor and the second end of the first capacitor is the third end of the driving filter unit.

[0013] In one embodiment, the threshold control unit comprises a Zener diode.

[0014] The cathode of the Zener diode is the first end of the threshold control unit, and the anode of the Zener diode is the second end of the threshold control unit.

[0015] In one embodiment, the dummy load is a resistor load.

[0016] In one embodiment, the output circuit comprises a first diode, a second diode, an inductor and a second capacitor.

[0017] The anode of the first diode is connected to the same end of the corresponding secondary winding, and the cathode of the first diode is connected to the cathode of the corresponding second diode and the first end of the corresponding inductor; the second end of the inductor is the positive output terminal of the corresponding secondary winding.

[0018] The anode of the second diode is connected to the opposite end of the corresponding secondary winding and is the negative output terminal of the corresponding secondary winding.

[0019] The second capacitor is connected between the positive output terminal and the negative output terminal.

[0020] The first end of the threshold control unit is connected to the cathode of the first diode corresponding to the target secondary winding.

[0021] In one embodiment, the output circuit comprises a first diode and a second capacitor.

[0022] The anode of the first diode is connected to the opposite end of the corresponding secondary winding, and the cathode of the first diode is the positive output terminal of the corresponding secondary winding.

[0023] The second capacitor is connected between the positive output terminal and the negative output terminal.

[0024] The first end of the threshold control unit is connected to the cathode of the first diode corresponding to the target secondary winding.

[0025] The second aspect of the embodiment of the utility model provides a switching power supply, comprising the open loop power supply circuit of accurate compensation as above first aspect or any embodiment in first aspect.

[0026] The embodiment of the utility model has the beneficial effect that compared with prior art:

[0027] The threshold control unit can control whether the dummy load works or not, the output voltage of the open-loop power supply circuit is higher when the load is light or empty than when the load is heavy, the adaptive load control circuit provided by the embodiment can stabilize the output voltage at the threshold voltage, after the actual load is put into use, the output voltage of the open-loop power supply circuit is lower than the threshold value, the adaptive load control circuit stops working, so that the dummy load does not work, additional loss is avoided, the power loss of the circuit is reduced, and the efficiency of the circuit is ensured. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to make the technical scheme in the embodiment of the utility model clearer, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description, obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained according to these drawings without creative labor.

[0029] Figure 1 It is the module schematic view of the open-loop power supply circuit of the precise compensation provided by the utility model embodiment;

[0030] Figure 2 It is the partial structure schematic view of the forward open-loop power supply circuit provided by the utility model embodiment;

[0031] Figure 3 It is the partial structure schematic view of the flyback open-loop power supply circuit provided by the utility model embodiment;

[0032] Figure 4 It is the partial structure schematic view of another flyback open-loop power supply circuit provided by the utility model embodiment;

[0033] Figure 5 It is the structure schematic view of the flyback open-loop power supply circuit provided by the utility model embodiment. DETAILED DESCRIPTION

[0034] In order to make the technical scheme in the embodiment of the utility model clearer, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description, obviously, the drawings in the following description are only some embodiments of the utility model, and for those skilled in the art, other drawings can also be obtained according to these drawings without creative labor.

[0035] The terms "comprise", "comprising", "include", "including" and any variations thereof in the Specification and in the Claims of the present application, as well as the terms "a", "an" and "the" used in the present application, are intended to cover both the singular and plural forms, thus including "but not limited to".

[0036] The present inventor finds that the existing switching power supply circuit, taking the multi-winding resistance of the flyback circuit as an example, the first secondary winding is used as feedback control, and the output of the other auxiliary circuit is output after being precisely stabilized by the LDO, which can ensure the steady voltage of each output in the design and ensure the normal operation of the LDO. Moreover, by minimizing the differential pressure, high working efficiency and low standby power consumption can be achieved. However, the cross regulation rate of the multi-output flyback power supply is poor, and when the main circuit or the auxiliary circuit works under dynamic load, the output of the other circuit or itself will be unstable, which makes the power supply work unreliable.

[0037] By adding a dummy load at each auxiliary winding, the output voltage can be stabilized, but adding a dummy load will also increase the power loss of the circuit, affecting the efficiency of the switching power supply circuit under full load.

[0038] In order to stabilize the output voltage and reduce the power loss of the circuit, in the embodiments of the present application, a threshold control unit is arranged to control the working state of the dummy load. When the load is light or empty, the dummy load can be connected to the circuit to stabilize the output voltage; when the actual load is stable, the dummy load can be disconnected to avoid power consumption.

[0039] The implementation of the present application will be described in detail below in combination with specific drawings:

[0040] Figure 1 A module schematic diagram of the open-loop power supply circuit with precise compensation provided by the embodiment of the present application is shown. For the convenience of description, only the parts related to the embodiment of the present application are shown, and the details are as follows:

[0041] As Figure 1 shown, the open-loop power supply circuit with precise compensation provided by the embodiment of the present application comprises a transformer, an adaptive load control circuit 1 and at least one output circuit 2. The transformer comprises at least one secondary winding, and the number of the secondary windings is the same as the number of the output circuits 2. Each secondary winding is connected to an actual load 3 through its corresponding output circuit 2. Figure 1 T1 in the above formula is a secondary winding, and T2 is a primary winding.

[0042] The adaptive load control circuit 1 comprises a threshold control unit 11, a driving filter unit 12, a switch tube Q1 and a dummy load Xz.

[0043] The first end of the threshold control unit 11 is connected to the output circuit 2 corresponding to the target secondary winding T1, wherein the target secondary winding T1 is one of the at least one secondary winding.

[0044] The second end of the threshold control unit 11 is connected to the first end of the driving filter unit 12, the second end of the driving filter unit 12 is connected to the first end of the switch tube Q1, and the third end of the driving filter unit 12 is connected to the negative output end of the target secondary winding T1.

[0045] The second end of the switch tube Q1 is connected to the positive output end of the target secondary winding T1 through the pseudo load Xz, and the third end of the switch tube Q1 is connected to the negative output end.

[0046] In the embodiment, the threshold control unit 11 can control whether the adaptive load control circuit 1 works or not. When the output voltage of the output circuit rises to the threshold of the threshold control unit 11, the threshold control unit 11 is turned on, and the first end of the switch tube Q1, i.e., the controlled end of the switch tube Q1, can be connected through the driving filter unit 12.

[0047] When the controlled end of the switch tube Q1 inputs current, the switch tube Q1 is turned on, so that the pseudo load Xz is connected to the circuit, and the adaptive load control circuit 1 works.

[0048] When the output voltage of the output circuit does not reach the threshold of the threshold control unit 11, the threshold control unit 11 is not turned on, the controlled end of the switch tube Q1 has no input current, and correspondingly, the switch tube Q1 is not turned on, so that the pseudo load is not connected to the circuit, i.e., the adaptive load control circuit 1 does not work, thereby avoiding increasing additional loss.

[0049] Here, the threshold control unit 11 can be a voltage stabilizing diode, a circuit network of a comparator, a reference voltage and a sampling resistor, or other circuits with the same function.

[0050] Optionally, the pseudo load Xz can be a resistance load.

[0051] The threshold control unit provided in the embodiment can control whether the pseudo load works or not. The output voltage of the open-loop power supply circuit is higher when the load is light or empty than when the load is heavy, and the adaptive load control circuit provided in the embodiment can make the output voltage stable at the threshold voltage. After the actual load is put into use, the output voltage of the open-loop power supply circuit is lower than the threshold value, the adaptive load control circuit exits the work, so that the pseudo load does not work, thereby avoiding increasing additional loss, reducing the power loss of the circuit, and ensuring the efficiency of the circuit.

[0052] Optionally, in this embodiment, the threshold control unit 11 includes a Zener diode Z1; the cathode of the Zener diode Z1 serves as the first terminal of the threshold control unit 11, and the anode of the Zener diode Z1 serves as the second terminal of the threshold control unit 11.

[0053] In this embodiment, the threshold control unit 11 can be implemented using Zener diode Z1. The cathode of Zener diode Z1 is connected to the output circuit 2, and the anode of Zener diode Z1 is connected to the drive filter unit 12. That is, Zener diode Z1 is reverse biased in the circuit.

[0054] When the reverse voltage does not reach the preset threshold voltage, the Zener diode Z1 is essentially not conducting. When the reverse bias voltage approaches the threshold voltage, the Zener diode Z1 begins to conduct and generates current. As the reverse bias voltage increases, the reverse current will also change, but the voltage across the Zener diode Z1 can be stabilized near the breakdown voltage.

[0055] Optionally, the driving filter unit 12 may include a first resistor R1, a second resistor R2, and a first capacitor C1; the first end of the first resistor R1 serves as the first end of the driving filter unit 12; the junction where the second end of the first resistor R1, the first end of the second resistor R2, and the first end of the first capacitor C1 are connected serves as the second end of the driving filter unit 12; and the junction where the second end of the second resistor R2 and the second end of the first capacitor C1 are connected serves as the third end of the driving filter unit 12.

[0056] In this embodiment, the threshold control unit 11 is connected to the controlled terminal of the switching transistor Q1 through the first resistor R1 to control the switching transistor Q1 to work or be turned off.

[0057] Here, the voltage across capacitor C1 is the voltage difference between the first and third terminals of switching transistor Q1.

[0058] When the open-loop power supply circuit is under light load or no load, the voltage across capacitor C1 will be less than the output voltage of the open-loop power supply circuit, thereby causing the switching transistor Q1 to work.

[0059] In some embodiments, the switching transistor Q1 can be a bipolar transistor operating in the amplification region. As the output voltage of the target secondary winding increases, the base current of the bipolar transistor increases, causing the voltage difference between the collector and emitter of the bipolar transistor to decrease, which in turn increases the current of the dummy load. Correspondingly, the higher the output voltage of the target secondary winding, the larger the current of the dummy load, and under the influence of the dummy load, the output voltage of the open-loop power supply circuit will decrease accordingly.

[0060] In the embodiment, by making the switch tube Q1 work in the amplification zone, the current flowing through the pseudo load can be dynamically changed with the output voltage overshoot size, so as to reduce the overall loss of the circuit.

[0061] Optionally, as shown in Figure 1 The switch tube can be an NPN triode, the collector voltage of the NPN triode is greater than the base voltage, and the base voltage is greater than the emitter voltage.

[0062] Correspondingly, the switch tube can also be a PNP triode, the emitter voltage of the PNP triode is greater than the base voltage, and the base voltage is greater than the emitter voltage.

[0063] In some embodiments, as shown in Figure 2 The output circuit 2 includes a first diode D1, a second diode D2, an inductor L1 and a second capacitor C2.

[0064] The anode of the first diode D1 is connected to the same end of the corresponding secondary winding, the cathode of the first diode D1 is connected to the cathode of the corresponding second diode D2 and the first end of the corresponding inductor; the second end of the inductor L1 is the output positive electrode of the corresponding secondary winding; the anode of the second diode D2 is connected to the opposite end of the corresponding secondary winding and is the output negative electrode of the corresponding secondary winding; the second capacitor C2 is connected between the output positive electrode and the output negative electrode; the first end of the threshold control unit 11 is connected to the cathode of the corresponding first diode D1 of the target secondary winding T1.

[0065] In the embodiment, the adaptive load control circuit 1 can be used in a forward circuit, and for the target secondary winding T1, the first end of the threshold control unit 11 can be connected to the cathode of the corresponding first diode D1.

[0066] In some embodiments, as shown in Figure 3 The output circuit 2 includes a first diode D1 and a second capacitor C2.

[0067] The anode of the first diode D1 is connected to the opposite end of the corresponding secondary winding, and the cathode of the first diode D1 is the output positive electrode of the corresponding secondary winding; the second capacitor C2 is connected between the output positive electrode and the output negative electrode; the first end of the threshold control unit 11 is connected to the cathode of the corresponding first diode D1 of the target secondary winding T1.

[0068] In the embodiment, the adaptive load control circuit 1 can be used in a flyback circuit, and for the target secondary winding T1, the first end of the threshold control unit 11 can be connected to the cathode of the corresponding first diode D1, and correspondingly, the first end of the threshold control unit 11 is also connected to the output positive electrode.

[0069] In some embodiments, the target secondary winding T1 can be a tapped winding, see Figure 4 Fig. 4 shows another partial structure diagram of a flyback open-loop power supply circuit, in which a tapped winding is shown as the target secondary winding T1, and the connection mode of the adaptive load control circuit 1 is shown.

[0070] In the present embodiment, the target secondary winding T1 includes three output terminals, such as OUT1, OUT2 and OUT3 in Fig. 4, and the adaptive load control circuit 1 can be connected between the first output terminal OUT2 and the second output terminal OUT3 to perform adaptive control of the dummy load. Here, the output terminal OUT3 can be grounded. Figure 4

[0071] Alternatively, the adaptive load control circuit 1 can also be connected between OUT1 and OUT2 to perform adaptive control of the dummy load between the first output terminal OUT1 and the second output terminal OUT2. When the output of the second output terminal OUT2 is heavy load, and the output of the first output terminal OUT1 is light load or no load, the dummy load is connected in the circuit to improve the stability of the output voltage of the first output terminal OUT1. Here, the output terminal OUT3 can be grounded.

[0072] The present embodiment considers that the output voltage of the open-loop power supply circuit is much higher when the circuit is in light load or no load than when the circuit is in heavy load, and by setting the adaptive load control circuit 1 provided by the present application, the output voltage in light load or no load can be stabilized at the threshold voltage; when the actual load is in use, the output voltage of the open-loop power supply circuit is lower than the threshold value, and the adaptive load control circuit 1 exits the work, avoiding additional loss in actual use.

[0073] And when the dynamic output voltage of the open-loop power supply circuit exceeds the range, by setting the adaptive load control circuit 1 provided by the present application, the output voltage in the dynamic process can be maintained at the threshold voltage, avoiding the transient overvoltage of the output voltage caused by the dynamic process, which damages the backend devices, and at the same time, the adaptive load control circuit 1 will not increase additional loss when it is in normal work.

[0074] The present application also provides a switching power supply, and for the details not described in detail, reference can be made to the corresponding circuit embodiments described above.

[0075] In some embodiments, the switching power supply can include a precisely compensated open-loop power supply circuit as in any of the above embodiments.

[0076] ​The above-described above embodiments are only used to illustrate the technical solutions of the present application, and are not limited thereto; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that the technical solutions recorded in the foregoing embodiments can still be modified, or some technical features therein can be replaced by equivalents; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. An open-loop power supply circuit with precision compensation, characterized in that, The adaptive load control circuit comprises a threshold control unit, a drive filter unit, a switch tube and a dummy load. The first end of the threshold control unit is connected to the output circuit corresponding to the target secondary winding. The second end of the threshold control unit is connected to the first end of the drive filter unit. The second end of the switch tube is connected to the positive output terminal of the target secondary winding through the dummy load.

2. The precisely compensated open-loop power supply circuit of claim 1, wherein, The switch tube comprises an NPN triode, the collector voltage of which is greater than the base voltage, and the base voltage is greater than the emitter voltage.

3. The precisely compensated open-loop power supply circuit of claim 1, wherein, The drive filter unit comprises a first resistor, a second resistor and a first capacitor. The first end of the first resistor is the first end of the drive filter unit. The joint of the second end of the first resistor, the first end of the second resistor and the first end of the first capacitor is the second end of the drive filter unit. The joint of the second end of the second resistor and the second end of the first capacitor is the third end of the drive filter unit.

4. The precisely compensated open-loop power supply circuit of claim 1, wherein, The threshold control unit comprises a Zener diode. The cathode of the Zener diode is the first end of the threshold control unit, and the anode of the Zener diode is the second end of the threshold control unit.

5. The precisely compensated open-loop power supply circuit of claim 1, wherein, The dummy load is a resistance load.

6. The precisely compensated open-loop power supply circuit of any of claims 1 to 5, wherein, The output circuit comprises a first diode, a second diode, an inductor and a second capacitor. The anode of the first diode is connected to the same end of the corresponding secondary winding, and the cathode of the first diode is connected to the cathode of the corresponding second diode and the first end of the corresponding inductor. The second end of the inductor is the positive output terminal of the corresponding secondary winding. The anode of the second diode is connected to the different end of the corresponding secondary winding and is the negative output terminal of the corresponding secondary winding. The second capacitor is connected between the positive output terminal and the negative output terminal.

7. The precisely compensated open-loop power supply circuit of any of claims 1 to 5, wherein, The first end of the threshold control unit is connected to the cathode of the first diode corresponding to the target secondary winding. The output circuit comprises a first diode and a second capacitor. The anode of the first diode is connected to the different end of the corresponding secondary winding, and the cathode of the first diode is the positive output terminal of the corresponding secondary winding. The second capacitor is connected between the positive output terminal and the negative output terminal.

8. A switching power supply, characterized by comprising: The first end of the threshold control unit is connected to the cathode of the first diode corresponding to the target secondary winding. The open-loop power supply circuit with precise compensation comprises the adaptive load control circuit as claimed in any one of claims 1 to 7.

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