PFC (Power Factor Correction) starting circuit and switching power supply

Abstract

The utility model provides a PFC starting circuit and a switching power supply. The PFC starting circuit comprises a power setting circuit and a switching circuit. The input end of the power setting circuit is connected with a control circuit of the switching power supply; the input end of the switching circuit is connected with the output end of the power setting circuit, and the output end of the switching circuit is connected with the PFC circuit of the switching power supply; and the power setting circuit controls the switching circuit to be switched on according to a control signal of the control circuit so as to start the PFC circuit. According to the utility model, the PFC circuit can be prevented from being synchronously conducted while the circuit is controlled to be conducted, and the standby power consumption of the switching power supply is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply, in particular to a PFC starting circuit and a switching power supply. Background Art

[0002] Some switching power supplies are provided with a PFC control circuit and a PWM control circuit, and the PFC control circuit and the PWM control circuit have their own independent control chips. Currently, most PFC control circuits will start when the PWM control circuit starts. Even if the switching power supply is in standby mode, the PFC control circuit will still start, increasing the standby power consumption of the switching power supply. Utility Model Content

[0003] The utility model provides a PFC starting circuit and a switching power supply, aiming to solve the problem of increased standby power consumption caused by the PFC control circuit of the current switching power supply starting up along with the starting up of the PWM control circuit.

[0004] In a first aspect, the utility model provides a PFC startup circuit, which includes a power setting circuit and a switch circuit; the input end of the power setting circuit is connected to the control circuit of the switching power supply; the input end of the switch circuit is connected to the output end of the power setting circuit, and the output end of the switch circuit is connected to the PFC circuit of the switching power supply; the power setting circuit controls the switching circuit to turn on according to a control signal of the control circuit to start the PFC circuit.

[0005] Furthermore, the switch circuit includes a first switch tube, a controlled end of the first switch tube is connected to the power setting circuit, a first pole of the first switch tube is connected to a power supply end, and a second pole of the first switch tube is connected to the PFC circuit.

[0006] Further, the power setting circuit includes a second switch tube, a first resistor, a second resistor, a third resistor, a first capacitor and a first diode; the positive electrode of the first diode is connected to the control circuit, the negative electrode of the first diode is respectively connected to one end of the first resistor and one end of the first capacitor, the other end of the first resistor and the other end of the first capacitor are both connected to one end of the second resistor, the other end of the second resistor is respectively connected to one end of the third resistor and the controlled end of the second switch tube, the other end of the third resistor and the first electrode of the second switch tube are both grounded, and the second electrode of the second switch tube is connected to the controlled end of the first switch tube.

[0007] Furthermore, it also includes a first filtering circuit and a second filtering circuit; one end of the first filtering circuit is connected to the first resistor, and the other end of the first filtering circuit is grounded; one end of the second filtering circuit is connected to the second resistor, and the other end of the second filtering circuit is grounded.

[0008] Furthermore, the first filtering circuit includes a second capacitor, one end of the second capacitor is connected to the first resistor, and the other end of the second capacitor is grounded.

[0009] Furthermore, the second filtering circuit includes a third capacitor, one end of the third capacitor is connected to the second resistor, and the other end of the third capacitor is grounded.

[0010] Furthermore, the switching circuit also includes a fourth resistor and a fifth resistor; one end of the fourth resistor is connected to the second switching tube, the other end of the fourth resistor is respectively connected to one end of the fifth resistor and the controlled end of the first switching tube, and the other end of the fifth resistor is connected to the power supply end.

[0011] Furthermore, the first switch tube is a triode, the base of the first switch tube is connected to the power setting circuit, the emitter of the first switch tube is connected to the power supply end, and the collector of the first switch tube is connected to the PFC circuit.

[0012] Furthermore, the second switch tube is a comparator, an input end of the comparator is connected to the second resistor, and an output end of the comparator is connected to a controlled end of the first switch tube.

[0013] In a second aspect, the utility model further provides a switching power supply, which includes a control circuit, a PFC circuit and any one of the above-mentioned PFC starting circuits.

[0014] The switching power supply disclosed by the utility model comprises a control circuit, a PFC circuit and a PFC starting circuit. The PFC starting circuit comprises a power setting circuit and a switch circuit. The power setting circuit is connected to the control circuit and is used to receive a control signal of the control circuit. When the output power of the power setting circuit satisfies the conduction power of the switch circuit, the switch circuit is turned on, thereby starting the PFC circuit, preventing the PFC circuit from being started synchronously when the control circuit is started, and reducing the standby power consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0016] Figure 1 It is a block diagram of a PFC startup circuit provided by an embodiment of the utility model;

[0017] Figure 2 It is a circuit diagram of a PFC startup circuit provided by an embodiment of the utility model. DETAILED DESCRIPTION

[0018] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0019] It should be understood that when used in this specification and the appended claims, the terms "include" and "comprises" indicate the presence of described features, integers, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integers, operations, elements, components and / or groups thereof.

[0020] It should also be understood that the terms used in this utility model specification are only for the purpose of describing specific embodiments and are not intended to limit the utility model. As used in the utility model specification and the appended claims, the singular forms of "a", "an" and "the" are intended to include plural forms unless the context clearly indicates otherwise. It should also be further understood that the term "and / or" used in the utility model specification and the appended claims refers to any combination of one or more of the associated listed items and all possible combinations, and includes these combinations.

[0021] In addition, the directional terms mentioned in the present invention, such as "upper", "lower", "front", "back", "left", "right", "inner", "outer", "side", etc., are only for reference to the directions of the attached drawings and the use status of the product. Therefore, the directional terms used are used to illustrate and understand the present invention, but not to limit the present invention. In addition, in the drawings, structures with similar or identical structures are represented by the same reference numerals.

[0022] See also Figure 1 to Figure 2 , Figure 1 1 is a block diagram of a PFC startup circuit 100 provided in an embodiment of the present utility model; Figure 2 FIG. 1 is a circuit diagram of a PFC startup circuit 100 provided in an embodiment of the present invention. Figure 1As shown, the PFC startup circuit 100 includes a power setting circuit 10 and a switch circuit 20; the input end of the power setting circuit 10 is connected to the control circuit 200 of the switching power supply; the input end of the switch circuit 20 is connected to the output end of the power setting circuit 10, and the output end of the switch circuit 20 is connected to the PFC circuit 300 of the switching power supply; the power setting circuit 10 controls the switch circuit 20 to turn on according to the control signal of the control circuit 200 to start the PFC circuit 300.

[0023] Specifically, the switching power supply may include a control circuit 200, a PFC circuit 300, and a PFC startup circuit 100. The control circuit 200 may be a PWM control circuit 200, which is used to control the operation of the switching power supply, and the control circuit 200 may also control the startup of the PFC circuit 300 through the PFC startup circuit 100. The PFC startup circuit 100 may include a power setting circuit 10 and a switch circuit 20, wherein an input end of the power setting circuit 10 is connected to the control circuit 200 for receiving a control signal of the control circuit 200. An output end of the power setting circuit 10 is connected to the switch circuit 20 for controlling the conduction of the switch circuit 20.

[0024] The switch circuit 20 is connected to the PFC circuit 300. When the switch circuit 20 is turned on, the control circuit 200 can control the PFC circuit 300 to start through the PFC start-up circuit 100. The power setting circuit 10 can set the output power of the switch circuit 20. When the output power output by the power setting circuit 10 meets the turn-on condition of the switch circuit 20, the switch circuit 20 is turned on, and the PFC circuit 300 is started.

[0025] As a further embodiment, the switch circuit 20 includes a first switch tube Q1, a controlled end of the first switch tube Q1 is connected to the power setting circuit 10, a first electrode of the first switch tube Q1 is connected to the power supply end, and a second electrode of the first switch tube Q1 is connected to the PFC circuit 300. Further, the first switch tube Q1 is a triode, a base of the first switch tube Q1 is connected to the power setting circuit 10, an emitter of the first switch tube Q1 is connected to the power supply end, and a collector of the first switch tube Q1 is connected to the PFC circuit 300. Further, the switch circuit 20 also includes a fourth resistor R4 and a fifth resistor R5; one end of the fourth resistor R4 is connected to the second switch tube Q2, the other end of the fourth resistor R4 is respectively connected to one end of the fifth resistor R5 and the controlled end of the first switch tube Q1, and the other end of the fifth resistor R5 is connected to the power supply end.

[0026] The switch circuit 20 may include a first switch tube Q1, a fourth resistor R4, and a fifth resistor R5. The first switch tube Q1 may be a triode, and the base of the first switch tube Q1 is connected to the power setting circuit 10, the emitter of the first switch tube Q1 is connected to the power supply end, and the collector of the first switch tube Q1 is connected to the PFC circuit 300. When the first switch tube Q1 is turned on, the PFC circuit 300 is turned on synchronously.

[0027] As a further embodiment, the power setting circuit 10 includes a second switch tube Q2, a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C1 and a first diode; the positive electrode of the first diode is connected to the control circuit 200, the negative electrode of the first diode is respectively connected to one end of the first resistor R1 and one end of the first capacitor C1, the other end of the first resistor R1 and the other end of the first capacitor C1 are both connected to one end of the second resistor R2, the other end of the second resistor R2 is respectively connected to one end of the third resistor R3 and the controlled end of the second switch tube Q2, the other end of the third resistor R3 and the first electrode of the second switch tube Q2 are both grounded, and the second electrode of the second switch tube Q2 is connected to the controlled end of the first switch tube Q1. Further, the second switch tube Q2 is a comparator, the input end of the comparator is connected to the second resistor R2, and the output end of the comparator is connected to the controlled end of the first switch tube Q1.

[0028] The power setting circuit 10 may include a first resistor R1, a second resistor R2, a third resistor R3 and a first capacitor C1. The first resistor R1, the second resistor R2, the third resistor R3 and the first capacitor C1 are used to set the output power. The output power can be adjusted by adjusting the values ​​of the first resistor R1, the second resistor R2, the third resistor R3 and the first capacitor C1, thereby adjusting the conduction threshold of the first switch tube Q1. The second switch tube Q2 may be a thyristor, and the controlled end of the second switch tube Q2 is connected to the second resistor R2, the positive electrode of the second switch tube Q2 is grounded, and the negative electrode of the second switch tube Q2 is connected to the first switch tube Q1. When the second switch Q2 is turned on, the first switch tube Q1 is turned on, and the PFC circuit 300 is turned on. The second switch tube Q2 can be a comparator, and the input end of the comparator is connected to the second resistor R2. When the voltage at the input end of the comparator is greater than a threshold value, both ends of the comparator are turned on, thereby controlling the first switch tube Q1 to be turned on. For example, the threshold value can be set to 2.5V, then when the voltage at the input end of the comparator is greater than 2.5V, both ends of the comparator are turned on.

[0029] As a further embodiment, it further includes a first filter circuit and a second filter circuit; one end of the first filter circuit is connected to the first resistor R1, and the other end of the first filter circuit is grounded; one end of the second filter circuit is connected to the second resistor R2, and the other end of the second filter circuit is grounded. Further, the first filter circuit includes a second capacitor C2, one end of the second capacitor C2 is connected to the first resistor R1, and the other end of the second capacitor C2 is grounded. Further, the second filter circuit includes a third capacitor C3, one end of the third capacitor C3 is connected to the second resistor R2, and the other end of the third capacitor C3 is grounded.

[0030] Among them, the first filter circuit and the second filter circuit are both used to filter out interference signals. The first filter circuit may include a second capacitor C2, and the second filter circuit may include a third capacitor C3. The second capacitor C2 is connected to the first resistor R1, and the third capacitor C3 is connected to the second resistor R2. Both are used to filter out interference signals. The ability to filter out interference signals can be adjusted by adjusting the capacity of the first capacitor C1 and the second capacitor C2.

[0031] The utility model also provides a switching power supply, which includes a control circuit 200, a PFC circuit 300 and a PFC starting circuit 100 according to any one of the above embodiments; the PFC starting circuit 100 includes a power setting circuit 10 and a switch circuit 20; the input end of the power setting circuit 10 is connected to the control circuit 200 of the switching power supply; the input end of the switch circuit 20 is connected to the output end of the power setting circuit 10, and the output end of the switch circuit 20 is connected to the PFC circuit 300 of the switching power supply; the power setting circuit 10 controls the switch circuit 20 to be turned on according to the control signal of the control circuit 200 so as to start the PFC circuit 300.

[0032] Specifically, the switching power supply may include a control circuit 200, a PFC circuit 300, and a PFC startup circuit 100. The control circuit 200 may be a PWM control circuit 200, which is used to control the operation of the switching power supply, and the control circuit 200 may also control the startup of the PFC circuit 300 through the PFC startup circuit 100. The PFC startup circuit 100 may include a power setting circuit 10 and a switch circuit 20, wherein an input end of the power setting circuit 10 is connected to the control circuit 200 for receiving a control signal of the control circuit 200. An output end of the power setting circuit 10 is connected to the switch circuit 20 for controlling the conduction of the switch circuit 20.

[0033] The switch circuit 20 is connected to the PFC circuit 300. When the switch circuit 20 is turned on, the control circuit 200 can control the PFC circuit 300 to start through the PFC start-up circuit 100. The power setting circuit 10 can set the output power of the switch circuit 20. When the output power output by the power setting circuit 10 meets the turn-on condition of the switch circuit 20, the switch circuit 20 is turned on, and the PFC circuit 300 is started.

[0034] The PFC starting circuit and the switching power supply disclosed by the utility model provide a PFC starting circuit between the control circuit and the PFC circuit, thereby preventing the PFC circuit from being started synchronously when the control circuit is started, thereby reducing the standby power consumption.

[0035] The above is only a specific implementation of the utility model, but the protection scope of the utility model is not limited thereto. Any technician familiar with the technical field can easily think of various equivalent modifications or replacements within the technical scope disclosed by the utility model, and these modifications or replacements should be included in the protection scope of the utility model. Therefore, the protection scope of the utility model should be based on the protection scope of the claims.

Claims

1. A PFC startup circuit, characterized in that: Applied to switching power supplies, including: A power setting circuit, wherein an input end of the power setting circuit is connected to a control circuit of the switching power supply; A switch circuit, wherein an input end of the switch circuit is connected to an output end of the power setting circuit, and an output end of the switch circuit is connected to a PFC circuit of the switching power supply; The power setting circuit controls the switch circuit to be turned on according to the control signal of the control circuit so as to start the PFC circuit.

2. The PFC startup circuit according to claim 1, characterized in that: The switch circuit includes a first switch tube, a controlled end of the first switch tube is connected to the power setting circuit, a first pole of the first switch tube is connected to the power supply end, and a second pole of the first switch tube is connected to the PFC circuit.

3. The PFC startup circuit according to claim 2, characterized in that: The power setting circuit includes a second switch tube, a first resistor, a second resistor, a third resistor, a first capacitor and a first diode; The anode of the first diode is connected to the control circuit, the cathode of the first diode is respectively connected to one end of the first resistor and one end of the first capacitor, the other end of the first resistor and the other end of the first capacitor are both connected to one end of the second resistor, the other end of the second resistor is respectively connected to one end of the third resistor and the controlled end of the second switch tube, the other end of the third resistor and the first electrode of the second switch tube are both grounded, and the second electrode of the second switch tube is connected to the controlled end of the first switch tube.

4. The PFC startup circuit according to claim 3, characterized in that: Also includes a first filtering circuit and a second filtering circuit; One end of the first filter circuit is connected to the first resistor, and the other end of the first filter circuit is grounded; One end of the second filter circuit is connected to the second resistor, and the other end of the second filter circuit is grounded.

5. The PFC startup circuit according to claim 4, characterized in that: The first filtering circuit includes a second capacitor, one end of the second capacitor is connected to the first resistor, and the other end of the second capacitor is grounded.

6. The PFC startup circuit according to claim 4, characterized in that: The second filtering circuit includes a third capacitor, one end of the third capacitor is connected to the second resistor, and the other end of the third capacitor is grounded.

7. The PFC startup circuit according to claim 3, characterized in that: The switch circuit further includes a fourth resistor and a fifth resistor; One end of the fourth resistor is connected to the second switch tube, the other end of the fourth resistor is respectively connected to one end of the fifth resistor and the controlled end of the first switch tube, and the other end of the fifth resistor is connected to the power supply end.

8. The PFC startup circuit according to claim 2, characterized in that: The first switch tube is a triode, the base of the first switch tube is connected to the power setting circuit, the emitter of the first switch tube is connected to the power supply end, and the collector of the first switch tube is connected to the PFC circuit.

9. The PFC startup circuit according to claim 3, characterized in that: The second switch tube is a comparator, the input end of the comparator is connected to the second resistor, and the output end of the comparator is connected to the controlled end of the first switch tube.

10. A switching power supply, characterized in that: The invention comprises a control circuit, a PFC circuit and a PFC starting circuit as claimed in any one of claims 1 to 9.

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