A control circuit for automatically converting current and a power adapter

Abstract

The utility model discloses a control circuit and power adapter of automatic conversion current relates to switching power adapter technical field, including rectifier input circuit, rectifier output circuit and operational amplifier circuit who connects gradually, the reference voltage input end and first voltage input end of operational amplifier circuit are connected the positive input end and negative input end of first operational amplifier respectively, and the output of first operational amplifier is connected the grid of MOS pipe, and the drain is connected the positive input end of second operational amplifier through the pull -down resistance network, the positive input end of third operational amplifier is connected to second voltage input, and the output of third operational amplifier is connected the negative input end of second operational amplifier through resistance, and the negative input end and positive input end of second operational amplifier are connected the photo -coupler for controlling current loop through the output of second operational amplifier after comparing, according to output voltage interval automatic switching maximum output current, reduce design complexity, promote charging stability and security.

Description

Technical Field

[0001] This utility model relates to the field of switching power supply adapter technology, and in particular to a control circuit and power adapter for automatic current conversion. Background Technology

[0002] The statements in this section are merely background information related to this utility model and do not necessarily constitute prior art.

[0003] With the continuous development of IoT technology and mobile electronic devices, power tools and other electric electronic products are being used more and more frequently. Since these products have built-in batteries and need to be charged frequently, it is necessary to monitor the output voltage and current for charging safety.

[0004] Currently, most methods for monitoring voltage and current use a software + microcontroller approach. This method requires developers to have high programming skills and a deep understanding of microcontroller hardware architecture. Not only do they need to write complex programs to implement voltage and current acquisition, analysis, and control algorithms, but they also need to handle various possible abnormal situations and interrupt events, which increases the difficulty of switching power supply design and the development cycle.

[0005] Furthermore, for different specifications of power tools, the suitable current range varies depending on the voltage operating range during charging. If a large current output is allowed at low voltage, the components in the circuit may be subjected to excessive power, resulting in severe overheating or even burnout. If the current and voltage are mismatched, electrical faults such as short circuits and arcing may occur. Utility Model Content

[0006] To address the aforementioned issues, this invention proposes an automatic current switching control circuit and power adapter that automatically switches the maximum output current based on the output voltage range, reducing design complexity and improving charging stability and safety.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, this utility model provides a control circuit for automatically switching current, comprising: The rectifier input circuit, rectifier output circuit, and operational amplifier circuit are connected in sequence. The input terminal of the rectifier input circuit is connected to the AC input voltage. The transformer output terminal of the rectifier output circuit is connected to the first voltage input terminal of the operational amplifier circuit. The voltage output terminal generated by the output current in the rectifier output circuit is connected to the second voltage input terminal of the operational amplifier circuit. The operational amplifier circuit includes a first operational amplifier, a second operational amplifier, and a third operational amplifier; The reference voltage input terminal and the first voltage input terminal of the operational amplifier circuit are connected to the positive input terminal and the negative input terminal of the first operational amplifier, respectively. The output terminal of the first operational amplifier is connected to the gate of the MOS transistor, and the drain is connected to the positive input terminal of the second operational amplifier through a pull-down resistor network. The second voltage input terminal is connected to the positive input terminal of the third operational amplifier. The output terminal of the third operational amplifier is connected to the negative input terminal of the second operational amplifier through a resistor. After comparing the negative and positive input terminals of the second operational amplifier, the output terminal of the second operational amplifier is connected to an optocoupler used to control the current loop.

[0008] Secondly, this utility model provides a power adapter, including: the automatic current switching control circuit described in the first aspect, for switching control of the maximum output current.

[0009] Compared with the prior art, the beneficial effects of this utility model are as follows: This invention provides an automatic current switching control circuit, comprising a rectifier input circuit, a rectifier output circuit, and an operational amplifier circuit connected in sequence. The rectifier input circuit converts the input AC voltage into DC voltage, which is then processed by power factor correction and resonance before being sent to the rectifier output circuit. In the rectifier output circuit, the voltage is filtered and rectified before being sent to the operational amplifier circuit. The operational amplifier circuit, through processing by a first operational amplifier, a second operational amplifier, and a third operational amplifier, achieves automatic switching of the maximum output current. The maximum output current is automatically switched according to the output voltage range without manual intervention. The adjustment of the maximum output current is achieved through hardware circuitry, reducing reliance on software algorithms, lowering design complexity, and improving charging stability and safety. It can adapt to different specifications of power tools and match load requirements or safety regulations under different voltage conditions.

[0010] Since different voltage operating ranges have different suitable current ranges, this invention provides an automatic current conversion control circuit that automatically adjusts the maximum output current based on the output voltage. This avoids overcurrent under unsuitable conditions, ensuring that the current remains within a safe and reasonable range under different voltage conditions, reducing the probability of electrical faults and protecting the circuit and equipment. For example, when the output voltage is in the 10V-15V range, the maximum current is automatically limited to 1A to prevent damage to the internal battery or other sensitive components due to excessive current.

[0011] The advantages of this invention in additional aspects will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the rectifier and filter circuit structure provided in Embodiment 1 of this utility model; Figure 2 This is a schematic diagram of the PFC circuit structure provided in Embodiment 1 of this utility model; Figure 3 This is a schematic diagram of the resonant circuit structure provided in Embodiment 1 of this utility model; Figure 4 This is a schematic diagram of the rectifier output circuit structure provided in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the chip power supply circuit structure provided in Embodiment 1 of this utility model; Figure 6 This is a schematic diagram of the PFC control circuit structure provided in Embodiment 1 of this utility model; Figure 7 This is a schematic diagram of the main control circuit structure provided in Embodiment 1 of this utility model; Figure 8 This is a schematic diagram of the loop feedback circuit structure provided in Embodiment 1 of this utility model; Figure 9 This is a schematic diagram of the operational amplifier circuit and operational amplifier power supply circuit provided in Embodiment 1 of this utility model; Figure 10 This is a schematic diagram of the operational amplifier circuit structure provided in Embodiment 1 of this utility model; Figure 11 This is a schematic diagram of the operational amplifier power supply circuit structure provided in Embodiment 1 of this utility model. Detailed Implementation

[0014] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0015] It should be noted that the following detailed description is exemplary and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0016] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments according to this utility model. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. Furthermore, it should be understood that the terms "comprising" and "including," and any variations thereof, are intended to cover non-exclusive inclusion, for example, a process, method, system, product, or apparatus that includes a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such process, method, product, or apparatus.

[0017] Where there is no conflict, the embodiments and features in the embodiments of this utility model can be combined with each other.

[0018] Example 1 This embodiment provides a control circuit for automatic current conversion, including: a rectifier input circuit, a rectifier output circuit, and an operational amplifier circuit connected in sequence; the input terminal of the rectifier input circuit is connected to an AC input voltage, the transformer output terminal of the rectifier output circuit is connected to the first voltage input terminal of the operational amplifier circuit, and the voltage output terminal generated by the output current in the rectifier output circuit is connected to the second voltage input terminal of the operational amplifier circuit. The operational amplifier circuit includes a first operational amplifier, a second operational amplifier, and a third operational amplifier; The reference voltage input terminal and the first voltage input terminal of the operational amplifier circuit are connected to the positive input terminal and the negative input terminal of the first operational amplifier, respectively. The output terminal of the first operational amplifier is connected to the gate of the MOS transistor, and the drain is connected to the positive input terminal of the second operational amplifier through a pull-down resistor network. The second voltage input terminal is connected to the positive input terminal of the third operational amplifier. The output terminal of the third operational amplifier is connected to the negative input terminal of the second operational amplifier through a resistor. After comparing the negative and positive input terminals of the second operational amplifier, the output terminal of the second operational amplifier is connected to an optocoupler used to control the current loop.

[0019] In this embodiment, the rectifier input circuit includes a rectifier filter circuit, a PFC circuit, and a resonant circuit connected in sequence.

[0020] In this embodiment, as Figure 1 As shown, the rectifier and filter circuit includes a filter circuit and a rectifier bridge. The input terminal of the filter circuit is connected to the AC input voltage, which is input through fuse F1. The filter circuit filters the AC input voltage and then inputs it to the rectifier bridge. The rectifier bridge is used to convert the filtered AC input voltage into DC voltage, and at the same time, it can supply power to the main control chip after rectification.

[0021] Specifically: The filter circuit includes a capacitor X (CX1) and a varistor MOV1 connected in parallel. One end of fuse F1 is connected to the power line L, and the other end is connected to one end of varistor MOV1. The other end of varistor MOV1 is connected to the power line N. The other end of varistor MOV1 is also connected to one end of fuse F2, and the other end of fuse F2 is connected to one end of capacitor X (CX1). The other end of capacitor X (CX1) is connected to one end of varistor MOV1, so that they are connected in parallel.

[0022] One end of capacitor X CX1 is connected to pin 1 of common mode inductor LF1, and the other end of capacitor X CX1 is connected to pin 4 of common mode inductor LF1. Pins 2 and 3 of common mode inductor LF1 are connected in parallel with capacitor X CX2.

[0023] X capacitor CX2 is also connected in parallel with series resistors R2 and R108. Series resistors R2 and R108 are connected in parallel with series resistors R1 and R107. Resistors R108 and R107 are connected together. The connection between X capacitor CX2 and resistor R2 is connected to the negative voltage V- through series Y capacitors CY1 and CY2.

[0024] In the series resistors R1 and R107, one end of resistor R1 is connected to pin 4 of common-mode inductor LF2, and the other end of resistor R1 is connected to one end of resistor R107. The other end of resistor R107 is connected to pin 1 of common-mode inductor LF2. Pins 2 and 3 of common-mode inductor LF2 are connected to rectifier bridge BD1. The AC input voltage is filtered by capacitors X1 and X2, common-mode inductor LF1, and common-mode inductor LF2 before being input to rectifier bridge BD1 for rectification. The rectifier bridge BD1 consists of four diodes and its main function is to convert AC to DC. Pins 2 and 3 of the common mode inductor LF2 are connected to the AC input terminals AC2 (pin 3 of rectifier bridge BD1) and AC1 (pin 2 of rectifier bridge BD1) of rectifier bridge BD1, respectively. Pin 1 (V-) of rectifier bridge BD1 is grounded, and pin 4 (V+, i.e., DC output terminal) of rectifier bridge BD1 is connected to the PFC circuit.

[0025] Pins 1 and 4 of the common mode inductor LF2 lead out to the L2 interface and N2 interface respectively, and pins 2 and 3 can also lead out to the L1 interface and N1 interface respectively.

[0026] In this filter circuit, X capacitors CX1 and CX2 are X capacitors in the safety capacitor category, and Y capacitors CY1 and CY2 are Y capacitors in the safety capacitor category. The X capacitors are connected across the two power lines (LN) to suppress differential mode interference; the Y capacitors are connected between the power line and the ground line (LE, NE) to suppress common mode interference.

[0027] In this embodiment, as Figure 2 As shown, the PFC circuit is connected to the DC voltage output from the rectifier bridge BD1 and performs power factor correction. Specifically, it includes the following circuit components: Pin 1 of inductor L1 is connected to the DC output terminal of rectifier bridge BD1 and one end of capacitor CBB CB1. The other end of capacitor CBB CB1 is connected to one end of capacitor CBB CB2 and grounded. The other end of capacitor CBB CB2 is connected to pin 2 of inductor L1 and leads out to the BD+ interface. CBB capacitor is a high-voltage film capacitor. Pin 2 of inductor L1 is connected to pin 4 of PFC inductor L3. Pin 6 of PFC inductor L3 is connected to the anode of diode D10 and grounded. The cathode of diode D10 is connected to the anode of diode D11. The cathode of diode D11 is led out to the VAUX interface. The cathode of diode D11 is also connected to pin 5 of PFC inductor L3 through capacitor C3 and parallel resistors R65 and R67; (pin 5 of PFC inductor L3 can also lead out to ZCD interface, but it is not used in this embodiment and will not be described in detail). Pin 1 of the PFC inductor L3 is connected to one end of the lead-bead resistor B1 and leads out to the DRAIN1 interface. The other end of the lead-bead resistor B1 is connected to the anode of the diode D8, and the cathode of the diode D8 is connected to the resonant circuit.

[0028] Pin 1 of inductor L1 is also connected to the anode of diode D7. The cathode of diode D7 is connected to one end of resistor R49. The other end of R49 is connected to one end of capacitor C1. The other end of capacitor C1 is connected to the cathode of diode D7. The cathode of diode D7 is led out to the VBUS interface through the thermistor NTC1.

[0029] The other end of the leaded bead resistor B1 is also connected to the drain of MOSFET Q1; the source of MOSFET Q1 is connected to one end of resistor R76 and leads out the current sensing voltage interface VCS; the other end of resistor R76 is connected to the gate of MOSFET Q1; the gate of MOSFET Q1 is also connected to the anode of diode D12; the cathode of diode D12 is connected to one end of resistor R73; the other end of resistor R73 is connected to one end of resistor R62; the other end of resistor R62 is connected to the anode of diode D12. The other end of the lead bead resistor B1 is also connected to the drain of MOSFET Q3. The source of MOSFET Q3 is connected to one end of resistor R79, and the other end of resistor R79 is connected to the gate of MOSFET Q3. The gate of MOSFET Q3 is also connected to the anode of diode D23. The cathode of diode D23 is connected to one end of resistor R77, and the other end of resistor R77 is connected to one end of resistor R34. The other end of resistor R34 is connected to the cathode of diode D23. One end of resistor R62 is connected to one end of resistor R77, and the connection is further connected to the GATE interface through resistors R91 and R94 in parallel.

[0030] The other end of the leaded bead resistor B1 is also connected to one end of capacitor C39. The other end of capacitor C39 is connected to the source of MOSFET Q3, and then grounded through parallel high-power alloy resistors RC1 and RC2, and the current detection voltage interface VCS is brought out.

[0031] The connection point between the leaded bead resistor B1 and the anode of diode D8 is connected to one end of capacitor C33. The other end of capacitor C33 is connected to one end of resistor R51, and the other end of resistor R51 is connected to the cathode of diode D8. The other end of resistor R51 is grounded through capacitor C38 and aluminum electrolytic capacitor EC1 connected in parallel; the positive terminal of aluminum electrolytic capacitor EC1 is connected to resistor R51, and the negative terminal of aluminum electrolytic capacitor EC1 is grounded.

[0032] The above PFC circuit performs power factor correction on the rectified DC voltage through L1, L3, D8 and Q1. In this embodiment, as Figure 3 As shown, the resonant circuit includes MOSFET Q5 and MOSFET Q6, and specifically includes the following circuit structure.

[0033] The gate of MOSFET Q5 is connected to the anode of diode D14. The cathode of diode D14 is connected to one end of resistor R70. The other end of resistor R70 is connected to one end of resistor R52 and one end of resistor R69. The other end of resistor R52 is connected to the anode of diode D14. The other end of resistor R69 is led out to the HG interface. The gate of MOSFET Q5 is also connected to one end of resistor R71. The other end of resistor R71 is connected to the source of MOSFET Q5 and one end of capacitor C34. The other end of capacitor C34 is connected to the drain of MOSFET Q5 and one end of leaded bead resistor B7. The other end of leaded bead resistor B7 is connected to the negative terminal of diode D8 in PFC circuit. The other end of capacitor C34 is also grounded through capacitor C35.

[0034] The gate of MOSFET Q6 is connected to the anode of diode D15. The cathode of diode D15 is connected to one end of resistor R78. The other end of resistor R78 is connected to one end of resistor R75 and one end of resistor R44. The other end of resistor R75 is connected to the anode of diode D15. The other end of resistor R44 is led out to the LG interface. The gate of MOSFET Q6 is also connected to one end of resistor R48. The other end of resistor R48 is connected to the source of MOSFET Q6 and one end of capacitor C41. The other end of capacitor C41 is connected to the drain of MOSFET Q6 and one end of leaded bead resistor B8. The other end of leaded bead resistor B8 is connected to the source of MOSFET Q5 and one end of inductor L2, and leads out to the HB interface. The connection between resistor R48 and capacitor C41 is connected to the negative terminal of aluminum electrolytic capacitor EC1 in the PFC circuit and grounded.

[0035] The other end of inductor L2 is connected to capacitor C37 in parallel and pin 1 of transformer winding T1A. Pin 2 of transformer winding T1A is connected to resonant capacitor CR (using metallized thin film capacitor) and leads out VCR interface. Resonant capacitor CR is connected to the source of MOSFET Q6.

[0036] In the above resonant circuit, by controlling the switching of MOSFETs Q5 and Q6, L2, T1 and CR are made to start resonant operation.

[0037] In this embodiment, as Figure 4 As shown, the rectifier output circuit includes a filter output circuit and a rectifier output control circuit; the filter output circuit includes multi-channel MOSFET chips Q13, Q14, Q15, and Q16 (i.e., chips integrating multiple MOSFETs), and the rectifier output control circuit includes a rectifier output control chip U3.

[0038] Specifically: The interface FA after the drain of the multi-channel MOSFET chip Q13 is connected to the drain of the multi-channel MOSFET chip Q14 is connected to pin 8 of the secondary winding T1C, the series resistor R80 and capacitor C28, and the VDA pin of the rectifier output control chip U3 through resistor R86. Capacitor C28 connects the source of multi-channel MOSFET chip Q13 to the source of multi-channel MOSFET chip Q14, and the source of multi-channel MOSFET chip Q13 is connected to the source of multi-channel MOSFET chip Q14. The gate of the multi-channel MOSFET chip Q13 is connected to the gate of the multi-channel MOSFET chip Q14 through resistors R81 and R82, and the connection point of resistors R81 and R82 is connected to the VGA pin of the rectifier output control chip U3.

[0039] The interface FC, after the drain of the multi-channel MOSFET chip Q15 is connected to the drain of the multi-channel MOSFET chip Q16, is connected to pin 13 of the secondary winding T1D, the series resistor R83 and capacitor C31, and is connected to the VDB pin of the rectifier output control chip U3 through resistor R88; T1C and T1D are both transformer outputs. Capacitor C31 connects the source of multi-channel MOSFET chip Q15 to the source of multi-channel MOSFET chip Q16, and the source of multi-channel MOSFET chip Q15 is connected to the source of multi-channel MOSFET chip Q16. The gate of the multi-channel MOSFET chip Q15 is connected to the gate of the multi-channel MOSFET chip Q16 through resistors R84 and R85, and the connection point of resistors R84 and R85 is connected to the VGB pin of the rectifier output control chip U3.

[0040] One of the sources of the multi-channel MOSFET chip Q14 is connected to one of the sources of the multi-channel MOSFET chip 15 through capacitors C29 and C30 connected in series, and this source is connected to the VSS pin of the rectifier output control chip U3.

[0041] The interface FB after connecting pin 10 of secondary winding T1C and pin 11 of secondary winding T1D is connected to the series connection of capacitor C29 and capacitor C30, and is also connected to aluminum electrolytic capacitors EC5, EC6 and EC7 in parallel through resistor R74. Resistor R74 is also connected to the source of multi-channel MOS transistor chip 15. The positive terminals of aluminum electrolytic capacitors EC5, EC6, and EC7 are connected in parallel to output a 29V+ voltage. This voltage is connected to the operational amplifier power supply circuit and regulated to 12V through Q12, ZD4, R122, and R221 to power U202. The negative terminals of aluminum electrolytic capacitors EC5, EC6, and EC7 are connected in parallel to resistor R74, and the voltage generated by the output current is connected through the parallel high-power alloy resistor RS1 and capacitor C2 (output terminal VRS1 is the voltage generated by the output current).

[0042] Meanwhile, the common-mode inductor LF3 filters the output. The positive terminals of electrolytic capacitor EC5, aluminum electrolytic capacitor EC6, and aluminum electrolytic capacitor EC7 are connected in parallel to the input pin 1 of the common-mode inductor LF3. The output terminal of the high-power alloy resistor RS1 and capacitor C2 connected in parallel is connected to the input pin 4 of the common-mode inductor LF3. Output pins 2 and 3 output the voltage.

[0043] The OTW pin (over-temperature protection check pin) of the rectifier output control chip U3 is output through resistor R89. The VCC pin is connected to capacitor C32 and resistor R87. Resistor R87 also outputs voltage through the Zener diode ZD8.

[0044] In the above rectifier output circuit, the secondary windings T1C and T1D are applied to Q13, Q14, Q15, Q16, EC5, EC6, EC7, and LF3 through a transformer. The switching of Q13, Q14, Q15, and Q16 is controlled through the VGA and VGB pins of U3 to perform rectification and filtering output, thereby realizing DC to DC transformer output and providing operating voltage for the operational amplifier circuit.

[0045] In this embodiment, the automatic current conversion control circuit further includes a PFC control circuit, a main control circuit, and a chip power supply circuit; the PFC control circuit includes a PFC control chip U4, and the main control circuit includes a main control chip U2.

[0046] Specifically: like Figure 5 As shown, the chip power supply circuit includes a transformer auxiliary winding T1B, which transforms and supplies power to U2; pin 4 of the transformer auxiliary winding T1B is connected to the anode of diode D16 and one end of capacitor C43, pin 6 is connected to the anode of diode D17 and one end of capacitor C44, and pin 5 is connected to the other end of capacitor C43 and the other end of capacitor C44 and grounded. The cathode of diode D16 is connected to one end of resistor R93, the other end of resistor R93 is connected to the positive terminal of aluminum electrolytic capacitor EC3, and the other end of resistor R93 is connected to the cathode of diode D17 through resistor R50. The negative terminal of aluminum electrolytic capacitor EC3 is connected to pin 5, and the positive terminal of aluminum electrolytic capacitor EC3 is led out to the VAUX interface.

[0047] The positive terminal of aluminum electrolytic capacitor EC3 is connected to one end of resistor R150 and the collector of transistor Q10. The other end of resistor R150 is connected to one end of resistor R152. The other end of resistor R152 is connected to the negative terminal of Zener diode ZD7 and one end of resistor R151. The other end of resistor R151 is connected to the base of transistor Q10. The emitter of transistor Q10 is connected to the positive terminal of diode D18. The emitter of transistor Q10 is connected to the collector of transistor Q10 through resistor R105. The positive terminal of Zener diode ZD7 is connected to the negative terminal of aluminum electrolytic capacitor EC2 and grounded. The positive terminal of aluminum electrolytic capacitor EC2 is connected to the negative terminal of diode D18 and leads out to the VCC interface. The VCC interface is connected to the VCC pin of the main control chip U2. The transformer auxiliary winding T1B supplies power to the VCC pin of the main control chip U2 after rectification by D16 and D17.

[0048] like Figure 6 As shown, the FB pin of the PFC control chip U4 is connected to the BIBO pin of U2 through a series resistor R97 and a resistor R47. The FB pin of the PFC control chip U4 is connected to the VBUS interface of the thermistor NTC1 in the PFC circuit through series resistors R96, R95 and R92. The FB pin of the PFC control chip U4 is grounded through a parallel connection of capacitor C49, resistor R64 and resistor R103, and resistor R96 is connected to capacitor C49.

[0049] Pin 3 of the PFC control chip U4 is connected to resistors R110, R10, and R109 in series. The other end of resistor R109 is connected to the cathodes of diodes D1 and D4 in parallel. The anode of diode D1 is connected to the L2 interface from pin 1 of the common mode inductor LF2 in the rectifier filter circuit, and the cathode of diode D4 is connected to the N2 interface from pin 4 of the common mode inductor LF2 in the rectifier filter circuit. The other end of resistor R109 is also connected to the main control chip U2 through resistor R72. Pin 3 of the PFC control chip U4 is grounded through a parallel capacitor C48, a resistor R63, and a resistor R102, and resistor R110 is connected to the parallel capacitor C48, a resistor R63, and a resistor R102.

[0050] The VCS pin of the PFC control chip U4 is grounded through capacitor C50 and connected to the VCS interface in the PFC circuit through resistor R100.

[0051] The VALY pin of the PFC control chip U4 is grounded through capacitor C47; the VALY pin of the PFC control chip U4 is connected to one end of resistor R104 and one end of resistor R99, the other end of resistor R104 is connected to bidirectional trigger diode D21, resistor R101 and ground; the other end of resistor R99 is connected to bidirectional trigger diode D21 and resistor R10 and then connected to the BRAIN1 interface in the PFC circuit through capacitor C45.

[0052] The GND pin of the PFC control chip U4 is grounded and connected to the VCCP pin of the main control chip U2 through capacitor C46. The GND pin of the PFC control chip U4 controls the switching of the MOSFET Q1 in the PFC circuit to improve the power factor PF value.

[0053] The VCC pin of the PFC control chip U4 is connected to the VCCP pin of the main control chip U2; the GATE pin of the PFC control chip U4 is connected to the GATE interface in the PFC circuit.

[0054] like Figure 7As shown, the HV pin of the main control chip U2 is connected to the BD+ interface in the PFC circuit through a series of resistors R55, R54, R53 and diode D20. The BD+ interface is connected to the positive terminal of diode D20, the negative terminal of diode D20 is connected to resistor R53, and is connected to the PFC control circuit through a connecting resistor R72.

[0055] The BIBO pin of the main control chip U2 is connected to the PFC control circuit through resistor R47; it is also grounded through parallel resistor R68 and capacitor C27.

[0056] The SETA pin of the main control chip U2 is grounded through a parallel capacitor C40 and a resistor R56.

[0057] The VFB pin of the main control chip U2 is connected to the phototransistor PC2B in the parallel optocoupler PC2 and the phototransistor PC1B in the optocoupler PC1 through resistor R41 and grounded; the VFB pin of the main control chip U2 is also grounded through capacitor C26.

[0058] The ISEN pin of the main control chip U2 is connected to the VCR interface of the resonant circuit through a series resistor R60 and a capacitor C51; the ISEN pin of the main control chip U2 is grounded through a capacitor C24; the ISEN pin of the main control chip U2 is grounded through a series resistor R60 and a resistor R57.

[0059] The PROT pin of the main control chip U2 is grounded through capacitor C52, and is also connected to resistor R58 and grounded through parallel resistor R66 and thermistor NTC7; the PROT pin of the main control chip U2 is also connected to the VAUX interface in the PFC circuit through series Zener diode ZD6 and resistor R106.

[0060] The SETB pin of the main control chip U2 is grounded through a parallel capacitor C53 and a resistor R59.

[0061] The VCCP pin of the main control chip U2 is connected to the PFC control circuit and is also grounded through capacitor C36.

[0062] The VCC pin of the main control chip U2 is grounded through capacitor C21; the VCC pin of the main control chip U2 is connected to the BST pin of the main control chip U2 through a series resistor R61 and diode D19; the VCC pin of the main control chip U2 is connected to the VCC interface of the chip power supply circuit.

[0063] The GND pin of the main control chip U2 is grounded.

[0064] The LG pin of the main control chip U2 is connected to the LG interface in the resonant circuit.

[0065] The HG pin of the main control chip U2 is connected to the HG interface in the resonant circuit.

[0066] The HB pin of the main control chip U2 is connected to the BST pin of the main control chip U2 through capacitor C22; capacitor C22 is connected to the output terminal of diode D19, and the HB pin of the main control chip U2 is connected to the HB interface in the resonant circuit.

[0067] The LG and HG pins of the main control chip U2 are used to control the switches of MOSFETs Q5 and Q6 in the resonant circuit. By controlling Q5 and Q6, L2, T1, and CR in the resonant circuit are made to resonate.

[0068] The main control circuit described above connects to the PFC circuit, resonant circuit, rectifier filter circuit, and PFC control circuit to control the operation of each circuit.

[0069] In this embodiment, the control circuit for the automatic current conversion also includes a loop feedback circuit, such as... Figure 8 As shown, it specifically includes: The reference pin R of the TL431 integrated chip U1 is connected to the positive voltage (29V+) through parallel resistors R13 and R7. The reference pin R of the TL431 integrated chip U1 is connected to the anode A of the TL431 integrated chip U1 through resistor R19 and grounded; The reference pin R of the TL431 integrated chip U1 is connected to the cathode K of the TL431 integrated chip U1 through capacitor C58; The reference pin R of the TL431 integrated chip U1 is connected to the cathode K of the TL431 integrated chip U1 through a parallel capacitor C20 and a resistor R125.

[0070] The cathode K of the TL431 integrated chip U1 is connected to the cathode of the light-emitting diode PC2A in the optocoupler PC2, and is connected to the anode of the light-emitting diode PC2A through resistor R12; The anode of the LED PC2A is connected to the anode of the Zener diode ZD3 through resistor R9, and the cathode of the Zener diode ZD3 is connected to the positive voltage (29V+). The light-emitting diode PC2A and the phototransistor PC2B in the main control circuit are packaged as an optocoupler PC2.

[0071] Among them, an optocoupler (or simply optocoupler) encapsulates a light-emitting device (light-emitting diode) and a photosensitive device (phototransistor, etc.) together. It is a device that transmits electrical signals through light signals and can achieve electrical isolation. It is often used in circuit isolation, level conversion, signal transmission and other scenarios. It can effectively suppress interference and ensure the safe and stable operation of the circuit.

[0072] The reference pin of U1 is supplied with voltage through R7 and R13. The potential of the reference pin of U1 is used to control the working mode of PC2A and the switching of PC2B. The purpose is to control the working state of the resonant circuit by controlling the VFB pin of U2.

[0073] In this embodiment, as Figures 9-10 As shown, the operational amplifier circuit converts current through a control current loop, including operational amplifier U202B (first operational amplifier), operational amplifier U202E (second operational amplifier) ​​and operational amplifier U202D (third operational amplifier). U202B is for control, U202E is for constant current, and U202D is for amplification.

[0074] Specifically: The negative input terminal (pin 6) of U202B is connected to the transformer output terminal (e.g., 29V+) of the rectifier output circuit through resistor R32. Resistor R32 is also connected to resistors R38, R37 and capacitor C17 in parallel. The other end of the parallel connection of resistors R38, R37 and capacitor C17 is grounded.

[0075] The positive input terminal (pin 5) of U202B is connected to a reference voltage (such as 2.5V+) through resistor R36. Resistor R36 is also connected to resistors R45, R46 and capacitor C19 in parallel. The other end of the parallel connection of resistors R45, R46 and capacitor C19 is grounded.

[0076] The output terminal (pin 7) of U202B is grounded through resistor R43; the output terminal of U202B is also connected to the gate of MOSFET Q4, the source of MOSFET Q4 is grounded, and the drain of MOSFET Q4 is connected to resistors R35 and R153 in parallel. The other end of resistors R35 and R153 in parallel is connected to 2.5V+ through resistor R33. The other ends of the parallel resistors R35 and R153 are also connected to the positive input terminal (pin 12) of U202E through the parallel resistors R39, R40 and C18. The other end of the parallel resistors R39, R40 and C18 is grounded. The resistors R40, R39, R35 and R153 form a pull-down resistor network.

[0077] The positive input terminal (pin 10) of U202D is connected to the voltage generated by the output current (VRS1 interface) through resistor R26, and is also grounded through capacitor C14; The negative input terminal (pin 9) of U202D is connected to one end of capacitor C11. The other end of capacitor C11 is connected to one end of resistor R21 and ground. The other end of resistor R21 is connected to one end of capacitor C11 and connected to the output terminal (pin 8) of U202D through resistor R23. The output of U202D is connected to one end of resistor R27, and the other end of resistor R27 is connected to the VRS1 interface through resistor R127.

[0078] The other end of resistor R27 is connected to the negative input terminal (pin 13) of U202E through resistors R30, R29 and capacitor C16 in parallel. The other end of the parallel connection of resistors R30, R29 and capacitor C16 is grounded. The negative input terminal of U202E is connected to the output terminal (pin 14) of U202E through a series capacitor C13 and a resistor R28, and a capacitor C15 connected in parallel with them. The output terminal of U202E is connected to the cathode of diode D3 through resistor R31. The anode of diode D3 is connected to the cathode of Zener diode ZD1, and the anode of Zener diode ZD1 is grounded.

[0079] The anode of diode D3 is also connected to the cathode of LED PC1A in optocoupler PC1, and the OTW pin of rectifier output control chip U3 is also connected between the anode of diode D3 and the cathode of LED PC1A. The cathode of LED PC1A is also connected to the anode of LED PC1A through resistor R15. The anode of LED PC1A is connected to the operational amplifier power supply circuit through resistor R156 to access the 29V+ interface, and is connected to the operational amplifier power supply circuit through resistor R8. Either resistor R156 or resistor R8 can be used to power PC1A. The cathode of LED PC1A is connected to the anode of diode D2, the cathode of diode D2 is connected to one end of resistor R20, and the other end of resistor R20 is connected to the output terminal (pin 1) of U202A. The light-emitting diode PC1A and the phototransistor PC1B in the main control circuit are packaged as an optocoupler PC1.

[0080] The function of U202A is to provide overvoltage protection for the output. The positive input terminal (pin 3) of U202A is connected to resistor R22 through parallel resistors R24, R25 and capacitor C12. Resistor R22 is connected to the transformer output terminal 29V+. The other end of parallel resistors R24, R25 and capacitor C12 is grounded. The negative input terminal (pin 2) of U202A is connected to resistor R16 through a parallel capacitor C10, resistor R17 and resistor R18. Resistor R16 is connected to the reference voltage 2.5V+, and the other end of the parallel capacitor C10, resistor R17 and resistor R18 is grounded. The negative input terminal of U202A is connected to the output terminal of U202A through a series resistor R14 and a capacitor C8, and a parallel capacitor C9.

[0081] In this embodiment, the operating principle of the operational amplifier circuit includes: Constant current section: The voltage VRS1 generated by the current through RS1 is sent to pin 10 of U202D through resistor R26 for signal amplification and output from pin 8. The voltage output from pin 8 is sent to pin 13 of U202E through resistor R27. The reference voltage at pin 13 of U202E is compared with the reference voltage at pin 12. The current loop of optocoupler PC1A is controlled through pin 14 of U202E.

[0082] Automatic current switching section: When the output voltage is in the range of 15V~29V, the maximum output current is 8A; when the output voltage is in the range of 10V~15V, the maximum output current is 1A.

[0083] Specifically: When the output voltage is in the range of 15V~29V, the output voltage is delivered to pin 6 of U202B through resistor R32. The reference voltage of pin 5 is 2.5V provided by resistor R36. At this time, the voltage of pin 6 of U202B is higher than the reference voltage of pin 5. Therefore, pin 7 of U202B is at a high potential, so Q4 is in the conducting state. At this time, the pull-down resistor of pin 12 of U202E is composed of R40 / / R39 / / (R35 / / R153) in parallel. Because Q4 is conducting, the overall resistance value of the pull-down resistor of pin 12 becomes smaller. At this time, the maximum output current can be 8A.

[0084] When the output voltage is in the range of 10V~15V, the output voltage is delivered to pin 6 of U202B through resistor R32. The reference voltage of pin 5 is 2.5V provided by resistor R36. At this time, the voltage of pin 6 of U202B is lower than the reference voltage of pin 5. Therefore, pin 7 of U202B is at a low potential, so Q4 is in a non-conducting state. The pull-down resistor of pin 12 of U202E is composed of R40 / / R39 in parallel. Because Q4 is not conducting, the overall resistance value of the pull-down resistor of pin 12 is larger than the resistance value of R40 / / R39 / / (R35 / / R153) in parallel, causing the potential of pin 12 to rise. At this time, the maximum output current can be 1A, thereby achieving the function of automatic current conversion.

[0085] In this embodiment, the operational amplifier circuit is powered by an operational amplifier power supply circuit; such as Figure 9 and Figure 11 As shown, the power supply for the operational amplifier circuit includes an auxiliary winding T1E; T1E transformer supplies power to U202; The auxiliary winding T1E has port F1B connected to the anode of diode D5. The cathode of diode D5 is connected to one end of resistor R5. The other end of resistor R5 is connected to the cathode of diode D26 through resistor R126. The anode of diode D26 is connected to port F3A of auxiliary winding T1E.

[0086] The other end of resistor R5 is also connected to 29V+ through resistor R155, and connected to resistor R165 of the operational amplifier circuit; the other end of resistor R155 is connected to the positive terminal of aluminum electrolytic capacitor EC4, and the negative terminal of aluminum electrolytic capacitor EC4 is grounded; the positive terminal of aluminum electrolytic capacitor EC4 is connected to the collector of transistor Q12, one end of resistor R11, and one end of resistor R122.

[0087] The emitter of transistor Q12 is connected to the anode of diode D203. The cathode of diode D203 is connected to resistor R8 of the operational amplifier circuit. The cathode of diode D203 is also connected to the other end of resistor R11. The other end of resistor R11 is connected to the positive terminal of aluminum electrolytic capacitor EC8. The negative terminal of aluminum electrolytic capacitor EC8 is grounded. The base of transistor Q12 is grounded through a series resistor R221 and a Zener diode ZD4. The series connection between the leads of resistor R221 and Zener diode ZD4 is connected to the other end of resistor R122.

[0088] The positive terminal of aluminum electrolytic capacitor EC8 is connected to capacitors C4 and C6 in parallel. A resistor R6 is connected between one end of the parallel connection of capacitors C4 and C6. One end of resistor R6 is connected to the positive terminal of aluminum electrolytic capacitor EC8, and the other end is connected to pin 4 of U202C, thereby powering U202C. The other end of the parallel connection of capacitors C4 and C6 is connected to pin 11 of U202C and grounded. U202A-U202E are also powered through pin 4.

[0089] One end of resistor R6 is also connected to the 5V+ interface and one end of resistor R3. The other end of resistor R3 is connected to one end of resistor R4. The other end of resistor R4 is connected to the cathode and control electrode R of TL431 integrated chip U203. The anode of TL431 integrated chip U203 is grounded. The control electrode R of TL431 integrated chip U203 outputs a reference voltage of 2.5V and is grounded through capacitor C25.

[0090] The operating principle of the op-amp power supply circuit is as follows: the auxiliary winding T1E is rectified by D5 and D26 and regulated by Q12, R122, R221 and ZD4, and then supplies power to pin 4 of U202C through R6; the auxiliary winding T1B is rectified by D5 and D26 and regulated by Q12, R122, R221 and ZD4, and then supplies power to U203 through R3 and R4. The regulated 2.5V is then used as the reference voltage for the op-amp circuit.

[0091] Example 2 This embodiment provides a power adapter, including: the automatic current switching control circuit described in Embodiment 1, for switching control of the maximum output current.

[0092] Although the specific embodiments of the present utility model have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present utility model. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solution of the present utility model are still within the scope of protection of the present utility model.

Claims

1. A control circuit for automatically converting current, characterized in that, include: The rectifier input circuit, rectifier output circuit, and operational amplifier circuit are connected in sequence. The input terminal of the rectifier input circuit is connected to the AC input voltage, the transformer output terminal of the rectifier output circuit is connected to the first voltage input terminal of the operational amplifier circuit, and the voltage output terminal generated by the output current in the rectifier output circuit is connected to the second voltage input terminal of the operational amplifier circuit. The operational amplifier circuit includes a first operational amplifier, a second operational amplifier, and a third operational amplifier; The reference voltage input terminal and the first voltage input terminal of the operational amplifier circuit are connected to the positive input terminal and the negative input terminal of the first operational amplifier, respectively. The output terminal of the first operational amplifier is connected to the gate of the MOS transistor, and the drain is connected to the positive input terminal of the second operational amplifier through a pull-down resistor network. The second voltage input terminal is connected to the positive input terminal of the third operational amplifier. The output terminal of the third operational amplifier is connected to the negative input terminal of the second operational amplifier through a resistor. After comparing the negative and positive input terminals of the second operational amplifier, the output terminal of the second operational amplifier is connected to an optocoupler used to control the current loop.

2. The control circuit for automatic current conversion as described in claim 1, characterized in that, The operational amplifier circuit includes a first operational amplifier U202B, a second operational amplifier U202E, and a third operational amplifier U202D; The negative input terminal of U202B is connected to one end of resistor R32 through resistors R38, R37 and capacitor C17 in parallel, and the other end of resistor R32 is connected to the transformer output terminal. The positive input terminal of U202B is connected to one end of resistor R36 through resistors R45, R46 and capacitor C19 in parallel, and the other end of resistor R36 is connected to the reference voltage. The output of U202B is connected to the gate of MOSFET Q4. The source of MOSFET Q4 is grounded. The drain of MOSFET Q4 is connected to a parallel resistor R35 and a resistor R153. The other end of the parallel resistor R35 and a resistor R153 is connected to a reference voltage through a resistor R33. The other ends of the parallel resistors R35 and R153 are also connected to the positive input terminal of U202E through parallel resistors R39, R40 and capacitor C18, forming a pull-down resistor network composed of resistors R40, R39, R35 and R153.

3. The control circuit for automatic current conversion as described in claim 1, characterized in that, The operational amplifier circuit includes a first operational amplifier U202B, a second operational amplifier U202E, and a third operational amplifier U202D; The positive input terminal of U202D is connected to the voltage generated by the output current through resistor R26; The negative input terminal of U202D is connected to one end of capacitor C11, the other end of capacitor C11 is connected to one end of resistor R21 and ground, and the other end of resistor R21 is connected to one end of capacitor C11 and connected to the output terminal of U202D through resistor R23. The negative input terminal of U202E is connected to one end of resistor R27 through resistors R30, R29 and C16 in parallel, and the other end of resistor R27 is connected to the output terminal of U202D.

4. The control circuit for automatic current conversion as described in claim 1, characterized in that, The operational amplifier circuit includes a first operational amplifier U202B, a second operational amplifier U202E, and a third operational amplifier U202D; The output terminal of U202E is connected to the cathode of diode D3 through resistor R31. The anode of diode D3 is connected to the cathode of Zener diode ZD1. The anode of Zener diode ZD1 is grounded. The anode of diode D3 is also connected to the cathode of LED PC1A in optocoupler PC1, and a rectifier output circuit is connected between the anode of diode D3 and the cathode of LED PC1A. The cathode of LED PC1A is also connected to the anode of LED PC1A through resistor R15, and the anode of LED PC1A is connected to the operational amplifier power supply circuit through resistors R156 and R8. The light-emitting diode PC1A and the phototransistor PC1B in the main control circuit are packaged as an optocoupler PC1.

5. A control circuit for automatic current conversion as described in any one of claims 2-4, characterized in that, The voltage generated by the current is sent to the positive input terminal of U202D through resistor R26 for signal amplification and output from the output terminal. The output voltage is sent to the negative input terminal of U202E through resistor R27. The negative input terminal of U202E is compared with the reference voltage at the positive input terminal, and the current loop of optocoupler PC1 is controlled through the output terminal of U202E.

6. A control circuit for automatic current conversion as described in any one of claims 2-4, characterized in that, When the output voltage is in the range of 15V~29V, the output voltage is supplied to the negative input terminal of U202B through resistor R32. The reference voltage of the positive input terminal is 2.5V provided by resistor R36. At this time, the voltage at the negative input terminal of U202B is higher than the reference voltage at the positive input terminal. Therefore, the output terminal of U202B is at a high potential, so MOSFET Q4 is in the conducting state. At this time, the pull-down resistor at the positive input terminal of U202E is composed of R40 / / R39 / / (R35 / / R153) in parallel. Due to the conduction of MOSFET Q4, the overall resistance value of the pull-down resistor at the positive input terminal of U202E becomes smaller. At this time, the maximum output current is 8A.

7. A control circuit for automatic current conversion as described in any one of claims 2-4, characterized in that, When the output voltage is in the range of 10V~15V, the output voltage is supplied to the negative input terminal of U202B through resistor R32. The reference voltage of the positive input terminal is 2.5V provided by resistor R36. At this time, the voltage at the negative input terminal of U202B is lower than the reference voltage at the positive input terminal. Therefore, the output terminal of U202B is at a low potential, so MOSFET Q4 is in a non-conducting state. At this time, the pull-down resistor at the positive input terminal of U202E is composed of R40 / / R39 in parallel. Since MOSFET Q4 is not conducting, the overall resistance value of the pull-down resistor at the positive input terminal of U202E is larger than the resistance value of R40 / / R39 / / (R35 / / R153) in parallel, causing the potential at the positive input terminal of U202E to rise. At this time, the maximum output current is 1A.

8. The control circuit for automatic current conversion as described in claim 1, characterized in that, The control circuit for automatic current conversion also includes an operational amplifier power supply circuit for powering the operational amplifier circuit; the operational amplifier circuit power supply includes an auxiliary winding T1E; the port F1B of the auxiliary winding T1E is connected to the anode of diode D5, the cathode of diode D5 is connected to one end of resistor R5, the other end of resistor R5 is connected to the cathode of diode D26 through resistor R126, and the anode of diode D26 is connected to the port F3A of the auxiliary winding T1E. The other end of resistor R5 is also connected to 29V+ through resistor R155, which is connected to the operational amplifier circuit; the other end of resistor R155 is connected to the positive terminal of aluminum electrolytic capacitor EC4, and the positive terminal of aluminum electrolytic capacitor EC4 is connected to the collector of transistor Q12, one end of resistor R11, and one end of resistor R122. The emitter of transistor Q12 is connected to the anode of diode D203. The cathode of diode D203 is connected to the operational amplifier circuit and the other end of resistor R11. The other end of resistor R11 is connected to the positive terminal of aluminum electrolytic capacitor EC8. The base of transistor Q12 is grounded through a series resistor R221 and Zener diode ZD4. The series connection point of the leads of resistor R221 and Zener diode ZD4 is connected to the other end of resistor R122. The positive terminal of aluminum electrolytic capacitor EC8 is connected to capacitors C4 and C6 in parallel. A resistor R6 is connected between one end of the parallel connection of capacitors C4 and C6. One end of resistor R6 is connected to the positive terminal of aluminum electrolytic capacitor EC8, and the other end is connected to U202C, thereby supplying power to U202C.

9. The control circuit for automatic current conversion as described in claim 8, characterized in that, One end of resistor R6 is connected to the 5V+ interface and one end of resistor R3. The other end of resistor R3 is connected to one end of resistor R4. The other end of resistor R4 is connected to the TL431 integrated chip U203. The control electrode of the TL431 integrated chip U203 outputs a reference voltage of 2.5V.

10. A power adapter, characterized in that, Includes the control circuit for automatic current conversion as described in any one of claims 1-9.

Images