Valley filling circuit
By introducing a current limiting resistor and bootstrap circuit into the valley-filling circuit, controlling its connection with the input circuit, the problem of impact current during high and low voltage switching is solved, improving product reliability and reducing loss.
Patent Information
- Application Number
- CN202420634135.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-03-29
- Publication Date
- 2025-06-17
- Estimated Expiration
- 2034-03-29
AI Technical Summary
The valley-filling circuit in existing switching power supplies will generate impact current when switching high and low voltages, resulting in the transformer core saturation and damage to the switch tube.
A valley filling circuit is designed, including the first and second stage input circuits, current limiting resistors and bootstrap circuits. The drive circuit controls the connection between the current limiting resistor and the input circuit, and suppresses the impact current during high and low voltage switching.
It effectively avoids the impact current caused by high and low voltage switching, protects the transformer core and switch tube, improves product reliability, and reduces the loss of the valley filling circuit when low voltage input.
Smart Images
Figure CN222996229U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of electronic circuits, in particular to a valley filling circuit. Background Art
[0002] In both the civilian and industrial fields, it is often necessary to convert the alternating current of various power grids into direct current. In order to make the switching power supply meet the global power grid standards, the input voltage of the switching power supply needs to be designed as a wide-range input voltage. However, this not only brings difficulties to the design of the switching power supply, but also increases the difficulty of selecting the specifications of passive components in the circuit, increases the volume of the circuit and reduces the working efficiency of the product. At the same time, it also brings greater cost pressure. The input part of the switching power supply usually consists of a bridge rectifier circuit and a filter capacitor, both of which are non-linear devices. Due to the existence of a large-capacity electrolytic capacitor, the conduction angle of the diode in the bridge rectifier circuit becomes very narrow and only conducts at the peak part of the AC voltage input, resulting in serious distortion of the AC input current and turning it into a spike pulse. This current waveform contains a large number of harmonic components, which will not only affect the power grid, but also cause a large reduction in the active power and power factor. Moreover, the large-capacity input electrolytic capacitor has a poor transient response speed. When the main power circuit of the switching power supply uses a double-tube series scheme, there is a phenomenon of uneven transient voltage sharing in the main power switching tubes.
[0003] Please refer to Figure 1 , Figure 1 for the circuit diagram of the valley filling circuit in the existing switching power supply. Among them, the valley filling circuit includes capacitor C1, capacitor C2, diode D1, switching tube Q1, switching tube Q2, primary winding L1, primary winding L2, switching tube Q3, and switching tube Q4.
[0004] The valley filling circuit in the switching power supply has the characteristics of high-voltage series connection and low-voltage parallel connection. Please refer to Figure 2-1 , that is, under high-voltage input conditions, switching tubes Q3 and Q4 are turned off, and capacitor C1 and capacitor C2 form a series circuit to provide energy for the main power circuit and meet the high-voltage withstand requirements; please refer to Figure 2-2 . Under low-voltage input conditions, switching tubes Q3 and Q4 are turned on, and capacitor C1 and capacitor C2 are connected in parallel to increase the capacitance value of the input capacitor. In this way, not only the power factor (PF value) is improved during high-voltage input, but also the problem of large output voltage ripple during low-voltage input can be effectively reduced. However, the defect of this valley filling switching power supply is that when the input voltage switches from low voltage to high voltage and operates transiently, the input capacitors C1 and C2 switch from a parallel relationship to a series relationship. Although the voltages of capacitor C1 and capacitor C2 do not change suddenly, the current will change suddenly. As a result, a transient impact current is generated in the main power circuit of the valley filling circuit, and in severe cases, the magnetic core of the transformer winding the primary windings L1 and L2 will be saturated, resulting in damage to the switching tubes Q1 and Q2. Content of the Utility Model
[0005] In view of this, the purpose of the present utility model is to provide a valley filling circuit, which can avoid the impact current generated during the high-low voltage switching, so as to prevent the saturation of the transformer core and the damage of the switching tube.
[0006] To solve the above technical problems, the present utility model is realized through the following technical measures:
[0007] A valley filling circuit is used to connect with an input voltage. The valley filling circuit includes a first-stage input circuit, a second-stage input circuit, a third switching tube, a fourth switching tube, and a first diode. Among them, the input end of the first-stage input circuit is respectively connected to the positive input end of the valley filling circuit and the drain of the third switching tube. The output end of the first-stage input circuit is connected to the anode of the first diode and the drain of the fourth switching tube. The source of the third switching tube is connected to the cathode of the first diode and the input end of the second-stage input circuit. The output end of the second-stage input circuit and the source of the fourth switching tube are commonly connected to the reference ground. The valley filling circuit further includes a current limiting resistor and a bootstrap circuit. The current limiting resistor is connected in series with the first-stage input circuit or the second-stage input circuit. The bootstrap circuit includes a switching tube and a driving circuit. The switching tube is connected in parallel with the current limiting resistor. The driving circuit collects the voltage between the drain and source of the third switching tube or the fourth switching tube to obtain a sampling voltage, and the driving circuit converts the sampling voltage into a driving voltage for controlling the on or off of the switching tube, so as to control whether the current limiting resistor is connected to the first-stage input circuit and / or the second-stage input circuit.
[0008] Preferably, when the input voltage is low, the driving circuit controls the switching tube to turn on, so that the current limiting resistor is not connected to the first-stage input circuit and / or the second-stage input circuit; when the input voltage is high, the driving circuit controls the switching tube to turn off, so that the current limiting resistor is connected to the first-stage input circuit and / or the second-stage input circuit.
[0009] Preferably, the first-stage input circuit includes a first switching unit formed by a first primary winding and a first switching tube connected in series, and a first voltage equalizing unit connected in parallel with the first switching unit. One end of the first switching unit is used as the input end of the first-stage input circuit, and the other end of the first switching unit is used as the output end of the first-stage input circuit. The second-stage input circuit includes a second switching unit formed by a second primary winding and a second switching tube connected in series, and a second voltage equalizing unit connected in parallel with the second switching unit. One end of the second switching unit is used as the input end of the second-stage input circuit, and the other end of the second switching unit is used as the output end of the second-stage input circuit.
[0010] The input terminal of the first switching unit is connected to the drain of the third switching transistor. The output terminal of the first switching unit is respectively connected to the anode of the first diode and the drain of the fourth switching transistor. The cathode of the first diode is respectively connected to the source of the third switching transistor and the input terminal of the second switching unit. The output terminal of the second switching unit and the source of the fourth switching transistor are commonly connected to the reference ground.
[0011] Preferably, the driving circuit includes an auxiliary winding, a storage capacitor, a filtering capacitor, a second diode, and a third diode;
[0012] The same-named terminal of the auxiliary winding is connected to the positive electrode of the storage capacitor, and the different-named terminal of the auxiliary winding is connected to the negative electrode of the storage capacitor. The negative electrode of the storage capacitor is connected to the source of the third switching transistor and the cathode of the first diode. The positive electrode of the storage capacitor is connected to the anode of the second diode. The cathode of the second diode is connected to the cathode of the third diode. The anode of the third diode is connected to the drain of the third switching transistor. The anode and cathode of the third diode are connected in parallel with the gate-source of the switching transistor. The drain-source of the switching transistor is connected in parallel with both ends of the current-limiting resistor; the current-limiting resistor is connected in series between the positive input terminal and the input terminal of the first switching unit.
[0013] Preferably, the driving circuit includes an auxiliary winding, a storage capacitor, a filtering capacitor, a second diode, and a third diode;
[0014] The same-named terminal of the auxiliary winding and the positive electrode of the storage capacitor are connected to the anode of the second diode. The different-named terminal of the auxiliary winding and the negative electrode of the storage capacitor are connected to the source of the switching transistor, i.e., the input reference ground. The cathode of the second diode, the cathode of the third diode, and the first end of the filtering capacitor are connected to the gate of the switching transistor. The source of the switching transistor, the second end of the filtering capacitor, and the anode of the third diode are connected to the drain of the fourth switching transistor. The current-limiting resistor is connected in series between the output terminal of the first switching unit and the anode of the first diode.
[0015] Preferably, the first switching transistor and the second switching transistor are connected to synchronous driving signals; the third switching transistor and the fourth switching transistor are connected to another synchronous driving signal; the first voltage equalizing unit is composed of a first voltage equalizing capacitor, and the second voltage equalizing unit is composed of a second voltage equalizing capacitor.
[0016] Preferably, the valley filling circuit further includes a secondary winding circuit, and the secondary winding circuit has a secondary winding; the auxiliary winding, the first primary winding, the second primary winding, and the secondary winding share the same transformer core. The auxiliary winding, the first primary winding, and the second primary winding are of the same name, and the auxiliary winding and the secondary winding are of different names.
[0017] The present utility model also provides a valley filling circuit for connecting to an input voltage. The valley filling circuit includes N input circuits, a bootstrap circuit, and a current limiting resistor, where N is an even number greater than or equal to 2; the current limiting resistor is connected to the input circuits, the bootstrap circuit is connected to the current limiting resistor, and the bootstrap circuit is provided with a switching tube. The switching tube conducts when the input voltage is low to open the current limiting resistor, and the switching tube turns off when the input voltage is high to connect the current limiting resistor to each input circuit.
[0018] Compared with the prior art, a valley filling circuit of the present utility model has the following beneficial effects:
[0019] When the input voltage switches from low to high, the switching tube in the bootstrap circuit changes from conducting to turning off, and the input circuits at all levels change from a parallel relationship to a series relationship. The current limiting resistor is connected to each input circuit, and the impact current generated on the primary side is suppressed by introducing the current limiting resistor, thereby ensuring that the primary power device operates within a reliable range and greatly increasing the reliability of the product; when the input voltage is low, the switching tube conducts, so that the current limiting resistor is short-circuited, the total resistance value is reduced, and thus the loss of the valley filling circuit is reduced. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 is a schematic diagram of a conventional valley filling circuit.
[0021] Figure 2-1 is when the input voltage is low, Figure 1 a simplified schematic diagram of the valley filling circuit in
[0022] Figure 2-2 is when the input voltage is high, Figure 1 a simplified schematic diagram of the valley filling circuit in
[0023] Figure 3 is a circuit schematic diagram of the valley filling circuit of the present utility model.
[0024] Figure 4 is a circuit schematic diagram of the first embodiment of the valley filling circuit of the present utility model.
[0025] Figure 5 is a circuit schematic diagram of the second embodiment of the valley filling circuit of the present utility model.
[0026] Figure 6 is a circuit schematic diagram of the third embodiment of the valley filling circuit of the present utility model.
[0027] Figure 7 is a circuit schematic diagram of the fourth embodiment of the valley filling circuit of the present utility model.
[0028] Figure 8 is a circuit schematic diagram of the fifth embodiment of the valley filling circuit of the present utility model.
[0029] Figure 9 This is the circuit schematic diagram of the sixth embodiment of the valley filling circuit of the present utility model. Specific embodiments
[0030] The present utility model / invention and its beneficial effects will be further described in detail below in conjunction with specific embodiments and the accompanying drawings of the specification. However, the specific embodiments of the present utility model / invention are not limited thereto.
[0031] Reference Figure 3 , the present utility model provides a valley filling circuit, which includes N-level input circuits, a first diode D1 (hereinafter simply referred to as diode D1), a third switching transistor Q3 (hereinafter simply referred to as switching transistor Q3), a fourth switching transistor Q4 (hereinafter simply referred to as switching transistor Q4), a bootstrap circuit, and a current limiting resistor R1. Among them, the input circuits are connected in series or in parallel, and N is an even number greater than or equal to 2.
[0032] Each level of input circuit includes a voltage equalizing unit and a switching unit. Each voltage equalizing unit is connected in parallel with the corresponding switching unit. The switching transistor Q3 is connected in parallel with the corresponding input circuit. The switching transistor Q4 is connected in parallel with the corresponding input circuit. Each level of switching unit is connected to a synchronous drive signal, and the switching transistors Q3 and Q4 are both connected to a synchronous drive signal.
[0033] The bootstrap circuit includes an auxiliary winding S1, a storage capacitor VCC (an electrolytic capacitor), a second diode D2 (hereinafter simply referred to as diode D2), a third diode D3 (hereinafter simply referred to as diode D3), a filter capacitor C4, and a switching transistor Q18. The auxiliary winding S1 and the secondary winding P1 share the same transformer core and are of opposite polarities. The primary windings L1 to Ln and the auxiliary winding S1 share the same transformer core and are of the same polarity. The storage capacitor VCC is connected in parallel with the auxiliary winding S1.
[0034] The input terminal of the first switching unit, the input terminal of the first voltage equalizing unit, and the drain of the switching transistor Q3 are commonly connected to the positive voltage terminal of the DC input voltage. The output terminal of the Nth switching unit, the output terminal of the Nth voltage equalizing unit, and the source of the switching transistor Q4 are commonly connected to the reference ground. The output terminal of the N / 2th switching unit, the output terminal of the N / 2th voltage equalizing unit, and the drain of the switching transistor Q4 are commonly connected to the anode of the diode D1. The cathode of the diode D1 is connected to the input terminal of the N / 2 + 1th switching unit, the input terminal of the N / 2 + 1th voltage equalizing unit, and the source of the switching transistor Q3.
[0035] The source of the switching transistor Q3 is connected with a bootstrap circuit. The bootstrap circuit samples the voltage between the drain and source of the switching transistor Q3, and combines the voltage signal generated by the auxiliary winding S1 to provide a driving voltage for the switching transistor Q18. The switching transistor Q18 controls the magnitude of the input current limiting resistor by conduction and cutoff to suppress the impact current brought by the high and low voltage switching, ensuring the reliability of the product.
[0036] The first embodiment
[0037] Figure 4 The figure is a schematic diagram of a valley filling circuit provided by the first embodiment of the present utility model. The valley filling circuit of this embodiment includes: a first-stage input circuit 10, a second-stage input circuit 20, a diode D1, a switching transistor Q3, a switching transistor Q4, a bootstrap circuit, a current-limiting resistor R1, a thermistor NTC, and a secondary winding circuit.
[0038] The input end of the first-stage input circuit 10 is connected to the positive input terminal VIN+ through the current-limiting resistor R1 and the thermistor NTC. The output end of the first-stage input circuit 10 is respectively connected to the anode of the diode D1 and the drain of the switching transistor Q4. The source of the switching transistor Q3 is respectively connected to the cathode of the diode D1 and the input end of the second-stage input circuit 20. The output end of the second-stage input circuit 20 and the source of the switching transistor Q4 are commonly connected to the reference ground.
[0039] Specifically, the first-stage input circuit 10 includes a first switching unit 101 formed by connecting a first primary winding L1 (hereinafter simply referred to as the primary winding L1) and a first switching transistor Q1 (hereinafter simply referred to as the switching transistor Q1) in series, and a first voltage equalizing unit (formed by a first voltage equalizing capacitor C1) connected in parallel with the first switching unit 101. One end of the first switching unit 101 serves as the input end of the first-stage input circuit 10 for connecting to the current-limiting resistor R1, and the other end of the first switching unit 101 serves as the output end of the first-stage input circuit 10 for connecting to the anode of the diode D1. The second-stage input circuit 20 includes a second switching unit 201 formed by connecting a second primary winding L2 (hereinafter simply referred to as the primary winding L2) and a second switching transistor Q2 (hereinafter simply referred to as the switching transistor Q2) in series, and a second voltage equalizing unit (formed by a second voltage equalizing capacitor C2) connected in parallel with the second switching unit 201. One end of the second switching unit 201 serves as the input end of the second-stage input circuit 20 for connecting to the cathode of the diode D1, and the other end of the second switching unit 201 serves as the output end of the second-stage input circuit 20 for connecting to the reference ground.
[0040] In this embodiment, the first voltage equalizing capacitor C1 and the second voltage equalizing capacitor C2 have the same parameter specifications; the primary winding L1 and the primary winding L2 share a magnetic core and are of the same name ends; the switching transistor Q1 and the switching transistor Q2 have the same parameter specifications, and the switching transistor Q3 and the switching transistor Q4 have the same parameter specifications.
[0041] The positive electrode of the first voltage-sharing capacitor C1, the first end of the primary winding L1, and the drain of the switching transistor Q3 are all connected to the positive input terminal VIN+ through the current-limiting resistor R1 and the thermistor NTC. The second end of the primary winding L1 is connected to the drain of the switching transistor Q1. The source of the switching transistor Q1, the negative electrode of the first voltage-sharing capacitor C1, and the drain of the switching transistor Q4 are commonly connected to the anode of the diode D1. The source of the switching transistor Q3, the positive electrode of the second voltage-sharing capacitor C2, and the first end of the primary winding L2 are commonly connected to the cathode of the diode D1. The second end of the primary winding L2 is connected to the drain of the switching transistor Q2. The source of the switching transistor Q2, the negative electrode of the second voltage-sharing capacitor C2, and the source of the switching transistor Q4 are commonly connected to the input reference ground.
[0042] The bootstrap circuit includes auxiliary windings S1 and S2 that share the same magnetic core with the primary windings L1 and L2 and are of the same name, a storage capacitor VCC, a discharge resistor R8, diodes D2 and D3, a filter capacitor C4, and a switching transistor Q18. Among them, the auxiliary windings S1, the storage capacitor VCC, the discharge resistor R8, the diodes D2 and D3, and the filter capacitor C4 form a drive circuit. The drive circuit is used to collect the voltage between the drain and source of the switching transistor Q3 to obtain a sampling voltage, and to convert the sampling voltage into a drive voltage for controlling the on or off of the switching transistor Q18, so as to control whether the current-limiting resistor R1 is connected to the first-stage input circuit 10 and / or the second-stage input circuit 20.
[0043] Specifically, the same-name end of the auxiliary winding S1, the first end of the discharge resistor R8, and the positive electrode of the storage capacitor VCC are connected to the anode of the diode D2. The opposite-name end of the auxiliary winding S1, the second end of the discharge resistor R8, and the negative electrode of the storage capacitor VCC are connected to the source of the switching transistor Q3. The cathode of the diode D2, the cathode of the diode D3, and the first end of the filter capacitor C4 are connected to the gate of the switching transistor Q18. The source and drain of the switching transistor Q18 are connected in parallel across the two ends of the current-limiting resistor R1.
[0044] The working principle of the circuit in this embodiment is as follows:
[0045] When the voltage input from the positive input terminal VIN+ of the valley filling circuit is a low voltage (i.e., when the input voltage is a low voltage), the control circuit controls the switch tubes Q3 and Q4 to conduct. The first switch unit 101 and the second switch unit 201 are also in a parallel relationship. The diode D1 is reversely cut off. At this time, the first voltage-sharing capacitor C1 and the second voltage-sharing capacitor C2 are in a parallel relationship, and the capacitance value of the input capacitor (i.e., the capacitance value of the parallel connection of the first voltage-sharing capacitor C1 and the second voltage-sharing capacitor C2) becomes larger. The input capacitor provides energy for the primary windings L1 and L2. The auxiliary winding S1 charges the energy storage capacitor VCC through the energy of the flyback-coupled secondary winding P1 and generates a positive voltage. Also, since the switch tube Q3 is in the conducting state, that is, the drain and source of the switch tube Q3 are at the same potential. At this time, the diode D2 conducts forward, and the voltage of the energy storage capacitor VCC provides the driving voltage for the switch tube Q18. The diode D3 and the filter capacitor C4 prevent the driving voltage of the switch tube Q18 from being too high and resist interference. The conduction of the switch tube Q18 shorts the input current-limiting resistor R1, and the total resistance value decreases to reduce the loss of the valley filling circuit.
[0046] When the voltage input from the positive input terminal VIN+ of the valley filling circuit is a high voltage, the control circuit controls the switch tubes Q3 and Q4 to turn off. The first switch unit 101 and the second switch unit 201 are in a series relationship. The diode D1 conducts forward. At this time, the first voltage-sharing capacitor C1 and the second voltage-sharing capacitor C2 are in a series relationship, and the capacitance value of the input capacitor becomes smaller (i.e., the capacitance value of the series connection of the first voltage-sharing capacitor C1 and the second voltage-sharing capacitor C2), and the total withstand voltage becomes larger. The input capacitor provides energy for the primary winding. The auxiliary winding S1 charges the energy storage capacitor VCC through the energy of the coupled secondary winding P1 and generates a positive voltage. Also, since the switch tube Q3 is in the off state, that is, the voltage between the drain and source of the switch tube Q3 is half of the voltage input from the positive input terminal VIN+ and is much larger than the voltage generated by the energy storage capacitor VCC. At this time, the diode D2 is reversely cut off, the source potential of the switch tube Q18 is greater than the gate potential, and the switch tube Q18 turns off. The total resistance of the valley filling circuit is the sum of the thermistor NTC1 and the current-limiting resistor R1, so as to suppress the inrush current brought by the switching of the input low voltage to high voltage of the switching power supply and greatly improve the reliability of the circuit.
[0047] Second Embodiment
[0048] As Figure 5The following is the schematic diagram of the valley filling circuit according to the second embodiment of the present invention. The valley filling circuit of this embodiment includes: a first-stage input circuit 10, a second-stage input circuit 20, a diode D1, a switching transistor Q3, a switching transistor Q4, a bootstrap circuit, a current-limiting resistor R1, a thermistor NTC, and a secondary winding circuit. The difference between the valley filling circuit in this embodiment and the valley filling circuit in the first embodiment is that the connection sequence between the switching transistor Q1 in the first switching unit 101 and the primary winding L1, and the connection sequence between the switching transistor Q2 in the second switching unit 201 and the primary winding L2 are different from those in the first embodiment.
[0049] Specifically, the positive electrode of the first voltage-sharing capacitor C1, the drain of the switching transistor Q1, and the drain of the switching transistor Q3 are all connected to the positive input terminal VIN+ through the current-limiting resistor R1 and the thermistor NTC. The source of the switching transistor Q1 is connected to the first end of the primary winding L1. The second end of the primary winding L1, the negative electrode of the first voltage-sharing capacitor C1, and the drain of the switching transistor Q4 are commonly connected to the anode of the diode D1. The source of the switching transistor Q3, the positive electrode of the second voltage-sharing capacitor C2, and the drain of the switching transistor Q2 are commonly connected to the cathode of the diode D1. The source of the switching transistor Q2 is connected to the first end of the primary winding L2. The second end of the primary winding L2, the negative electrode of the second voltage-sharing capacitor C2, and the source of the switching transistor Q4 are commonly connected to the input reference ground.
[0050] The working principle of the valley filling circuit in this embodiment is the same as that of the valley filling circuit in the first embodiment. Similarly, the valley filling circuit in this embodiment can also achieve the same effect as the first embodiment, and will not be described in detail here.
[0051] Third Embodiment
[0052] As Figure 6 The following is the schematic diagram of the valley filling circuit according to the third embodiment of the present invention. The difference between the valley filling circuit in this embodiment and the valley filling circuit in the first embodiment is that the first-stage input circuit 10 in this embodiment includes N switching units and N voltage-sharing units. The switching units at all levels are connected in series in sequence, and each voltage-sharing unit is connected in parallel with the corresponding switching unit. Similarly, the second-stage input circuit 20 includes N switching units and N voltage-sharing units. The switching units at all levels are connected in series in sequence, and each voltage-sharing unit is connected in parallel with the corresponding switching unit. N is an even number greater than or equal to 2, and it can also achieve the same effect as the first embodiment.
[0053] Fourth Embodiment
[0054] As Figure 7 The following is the schematic diagram of the valley filling circuit according to the fourth embodiment of the present invention. The difference between the valley filling circuit in this embodiment and the valley filling circuit in the first embodiment is that the connection relationship between the bootstrap circuit and the discharge resistor R8 and the first-stage input circuit 10 and the second-stage input circuit 20 in this embodiment is different from that in the first embodiment.
[0055] Specifically, the bootstrap circuit also includes auxiliary windings S1, energy storage capacitor VCC, discharge resistor R8, diode D2, diode D3, filter capacitor C4, and switching transistor Q18, which share the same magnetic core with the primary windings L1 and L2 and have the same name ends. Among them, the auxiliary winding S1, energy storage capacitor VCC, discharge resistor R8, diode D2, diode D3, and filter capacitor C4 form a drive circuit. The drive circuit is used to collect the voltage between the drain and source of the switching transistor Q4 to obtain a sampling voltage, and to convert the sampling voltage into a drive voltage for controlling the turning on or off of the switching transistor Q18, so as to control whether the current-limiting resistor R1 is connected to the first-stage input circuit 10 and / or the second-stage input circuit 20.
[0056] Specifically, the same name end of the auxiliary winding S1, the first end of the discharge resistor R8, and the positive electrode of the energy storage capacitor VCC are connected to the anode of the diode D2. The different name end of the auxiliary winding S1, the second end of the discharge resistor R8, and the negative electrode of the energy storage capacitor VCC are connected to the source of the switching transistor Q2, which is the input reference ground. The cathode of the diode D2, the cathode of the diode D3, and the first end of the filter capacitor C4 are connected to the gate of the switching transistor Q18. The source of the switching transistor Q18, the second end of the filter capacitor C4, and the anode of the diode D3 are connected to the drain of the switching transistor Q4. The current-limiting resistor R1 is connected in series between the output end of the first switching unit 101 and the anode of the diode D1.
[0057] The working principle of the valley filling circuit in this embodiment is the same as that of the valley filling circuit in the first embodiment. Similarly, the valley filling circuit in this embodiment can achieve the same effect as the first embodiment, and will not be described in detail here.
[0058] The Fifth Embodiment
[0059] As Figure 8 shown in the schematic diagram of the valley filling circuit of the fifth embodiment of the present invention, the difference between the valley filling circuit in this embodiment and the valley filling circuit in the first embodiment is that the first-stage input circuit 10 in this embodiment includes N switching units and N voltage equalizing units. The switching units at all levels are connected in series in sequence, and each voltage equalizing unit is connected in parallel with the corresponding switching unit. Similarly, the second-stage input circuit 20 may include N switching units and N voltage equalizing units. The switching units at all levels are connected in series in sequence, and each voltage equalizing unit is connected in parallel with the corresponding switching unit. N is an even number greater than or equal to 2, and it can also achieve the same effect as the first embodiment.
[0060] The Sixth Embodiment
[0061] As Figure 9The following shows the schematic diagram of the valley filling circuit according to the sixth embodiment of the present utility model. The difference between the valley filling circuit in this embodiment and that in the first embodiment is that the secondary output winding P1 and the auxiliary windings L1 and L2 in this embodiment are of the same name, and the auxiliary winding S1 and the primary windings L1 and L2 are of opposite names. The working principle of the valley filling circuit in this embodiment is the same as that in the first embodiment. Similarly, the valley filling circuit in this embodiment can achieve the same effect as that in the first embodiment, and will not be described in detail here.
[0062] The above are only the implementation manners of the present utility model. It should be particularly noted that the above implementation manners should not be regarded as limitations on the present utility model. For those of ordinary skill in the art, without departing from the above basic technical idea of the present utility model, various other forms of modifications, substitutions or changes can be made to the specific implementation circuit of the present utility model, all of which fall within the scope of the protection of the present utility model.
Claims
1. A valley filling circuit, used for connecting to an input voltage, the valley filling circuit comprising a first-stage input circuit (10), a second-stage input circuit (20), a third switch tube (Q3), a fourth switch tube (Q4) and a first diode (D1), wherein: the input end of the first-stage input circuit (10) is respectively connected to the positive input end (VIN+) of the valley filling circuit and the drain of the third switch tube (Q3), the output end of the first-stage input circuit (10) is connected to the anode of the first diode (D1) and the drain of the fourth switch tube (Q4), the source of the third switch tube (Q3) is connected to the cathode of the first diode and the input end of the second-stage input circuit (20), and the output end of the second-stage input circuit (20) and the source of the fourth switch tube (Q4) are commonly connected to a reference ground; characterized in that: The valley filling circuit further includes: A current limiting resistor (R1), the current limiting resistor (R1) being connected in series with the first-stage input circuit (10) or the second-stage input circuit (20); A bootstrap circuit, the bootstrap circuit comprising a switch tube (Q18) and a drive circuit, the switch tube (Q18) being connected in parallel with the current limiting resistor (R1), the drive circuit collecting the voltage between the drain and source of the third switch tube (Q3) or the fourth switch tube (Q4) to obtain a sampling voltage, and the drive circuit converting the sampling voltage into a drive voltage for controlling the switch tube (Q18) to be turned on or off, so as to control whether the current limiting resistor (R1) is connected to the first-stage input circuit (10) and / or the second-stage input circuit (20).
2. The valley filling circuit according to claim 1, characterized in that: When the input voltage is low, the drive circuit controls the switch tube (Q18) to be turned on, so that the current limiting resistor (R1) is not connected to the first-stage input circuit (10) and / or the second-stage input circuit (20); When the input voltage is high voltage, the drive circuit controls the switch tube (Q18) to be turned off, so that the current limiting resistor (R1) is connected to the first-stage input circuit (10) and / or the second-stage input circuit (20).
3. The valley filling circuit according to claim 1, characterized in that: The first-stage input circuit (10) comprises a first switch unit (101) formed by a first primary winding (L1) and a first switch tube (Q1) connected in series, and a first voltage balancing unit connected in parallel with the first switch unit (101); one end of the first switch unit (101) serves as an input end of the first-stage input circuit (10), and the other end of the first switch unit (101) serves as an output end of the first-stage input circuit (10); the second-stage input circuit (20) comprises a second switch unit (201) formed by a second primary winding (L2) and a second switch tube (Q2) connected in series, and a second voltage balancing unit connected in parallel with the second switch unit (201); one end of the second switch unit (201) serves as an input end of the second-stage input circuit (20), and the other end of the second switch unit (201) serves as an output end of the second-stage input circuit (20); The input end of the first switch unit (101) is connected to the drain of the third switch tube (Q3), the output end of the first switch unit (101) is respectively connected to the anode of the first diode (D1) and the drain of the fourth switch tube (Q4), the cathode of the first diode (D1) is respectively connected to the source of the third switch tube (Q3) and the input end of the second switch unit (201), and the output end of the second switch unit (201) and the source of the fourth switch tube (Q4) are commonly connected to a reference ground.
4. The valley filling circuit according to claim 3, characterized in that: The driving circuit comprises an auxiliary winding (S1), an energy storage capacitor (VCC), a filter capacitor (C4), a second diode (D2) and a third diode (D3); One end of the auxiliary winding (S1) is connected to the positive electrode of the energy storage capacitor (VCC), and the other end of the auxiliary winding (S1) is connected to the negative electrode of the energy storage capacitor (VCC). The negative electrode of the energy storage capacitor (VCC) is connected to the source of the third switch tube (Q3) and the cathode of the first diode (D1). The positive electrode of the energy storage capacitor (VCC) is connected to the anode of the second diode (D2). The cathode of the second diode (D2) is connected to the cathode of the third diode (D3). The anode of the third diode (D3) is connected to the drain of the third switch tube (Q3). The anode and cathode of the third diode (D3) are connected in parallel to the gate-source of the switch tube (Q18). The drain-source of the switch tube (Q18) is connected in parallel to the two ends of the current limiting resistor (R1); the current limiting resistor (R1) is connected in series between the positive input terminal (VIN+) and the input terminal of the first switch unit (101).
5. The valley filling circuit according to claim 3, characterized in that: The driving circuit comprises an auxiliary winding (S1), an energy storage capacitor (VCC), a filter capacitor (C4), a second diode (D2) and a third diode (D3); One end of the auxiliary winding (S1) and the positive electrode of the energy storage capacitor (VCC) are connected to the anode of the second diode (D2); the other end of the auxiliary winding (S1) and the negative electrode of the energy storage capacitor (VCC) are connected to the source of the second switch tube (Q2), i.e., the input reference ground; the cathode of the second diode (D2), the cathode of the third diode (D3), and the first end of the filter capacitor (C4) are connected to the gate of the switch tube (Q18); the source of the switch tube (Q18), the second end of the filter capacitor (C4), and the anode of the third diode (D3) are connected to the drain of the fourth switch tube (Q4); and the current limiting resistor (R1) is connected in series between the output end of the first switch unit (101) and the anode of the first diode (D1).
6. The valley filling circuit according to claim 3, characterized in that: The first switch tube (Q1) and the second switch tube (Q2) are connected to a synchronous drive signal; the third switch tube (Q3) and the fourth switch tube (Q4) are connected to another synchronous drive signal; the first voltage balancing unit is composed of a first voltage balancing capacitor (C1), and the second voltage balancing unit is composed of a second voltage balancing capacitor (C2).
7. The valley filling circuit according to claim 3, characterized in that: It also includes a secondary winding circuit, wherein the secondary winding circuit (30) has a secondary winding (P1); the drive circuit includes an auxiliary winding (S1); The auxiliary winding (S1), the first primary winding (L1), the second primary winding (L2), and the secondary winding (P1) share a same transformer core; the auxiliary winding (S1), the first primary winding (L1), and the second primary winding (L2) are mutually identical ends; and the auxiliary winding (S1) and the secondary winding (P1) are mutually opposite ends.
8. A valley filling circuit, used to connect to an input voltage, the valley filling circuit comprising N input circuits, N being an even number greater than or equal to 2, characterized in that: The invention also includes a bootstrap circuit and a current limiting resistor (R1), wherein the current limiting resistor (R1) is connected to the input circuit, the bootstrap circuit is connected to the current limiting resistor (R1), and the bootstrap circuit is provided with a switch tube (Q18). When the input voltage is low, the switch tube (Q18) is turned on to disconnect the current limiting resistor (R1), and when the input voltage is high, the switch tube (Q18) is turned off to connect the current limiting resistor (R1) to each of the input circuits.
9. The valley filling circuit according to claim 8, characterized in that: The N input circuits include a first-stage input circuit (10) and a second-stage input circuit (20), wherein the first-stage input circuit (10) includes a first switch unit (101) formed by a first primary winding (L1) and a first switch tube (Q1) connected in series, and a first voltage balancing unit connected in parallel with the first switch unit (101); and the second-stage input circuit (20) includes a second switch unit (201) formed by a second primary winding (L2) and a second switch tube (Q2) connected in series, and a second voltage balancing unit connected in parallel with the second switch unit (201).
10. The valley filling circuit according to claim 8, characterized in that: The bootstrap circuit comprises an auxiliary winding (S1), an energy storage capacitor (VCC), a filter capacitor (C4), a second diode (D2), a third diode (D3) and the switch tube (Q18); One end of the auxiliary winding (S1) is connected to the positive electrode of the energy storage capacitor (VCC), and the other end of the auxiliary winding (S1) is connected to the negative electrode of the energy storage capacitor (VCC). The negative electrode of the energy storage capacitor (VCC) is connected to the source of the third switch tube (Q3) and the cathode of the first diode (D1). The positive electrode of the energy storage capacitor (VCC) is connected to the anode of the second diode (D2). The cathode of the second diode (D2) is connected to the cathode of the third diode (D3). The anode of the third diode (D3) is connected to the drain of the third switch tube (Q3). The anode and cathode of the third diode (D3) are connected in parallel to the gate-source of the switch tube (Q18). The drain-source of the switch tube (Q18) is connected in parallel to the two ends of the current limiting resistor (R1). The current limiting resistor R1 is connected in series between the positive input terminal (VIN+) of the valley filling circuit and the input terminal of the first switch unit (101).
11. The valley filling circuit according to claim 8, characterized in that: The bootstrap circuit comprises an auxiliary winding (S1), an energy storage capacitor (VCC), a filter capacitor (C4), a second diode (D2), a third diode (D3) and the switch tube (Q18); One end of the auxiliary winding (S1) and the positive electrode of the energy storage capacitor (VCC) are connected to the anode of the second diode (D2); the other end of the auxiliary winding (S1) and the negative electrode of the energy storage capacitor (VCC) are connected to the source of the second switch tube (Q2), i.e., the input reference ground; the cathode of the second diode (D2), the cathode of the third diode (D3), and the first end of the filter capacitor (C4) are connected to the gate of the switch tube (Q18); the source of the switch tube (Q18), the second end of the filter capacitor (C4), and the anode of the diode (D3) are connected to the drain of the fourth switch tube (Q4); and the current limiting resistor (R1) is connected in series between the output end of the first switch unit (101) and the anode of the first diode (D1).