Switching power supply system and control chip

Abstract

The invention discloses a switching power supply system and a control chip, and the system comprises a fast charging power supply system. The fast charging power supply system comprises a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a resistor Rcs, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a transformer T1, a main controller chip U5, a stabilized voltage supply U4, an optocoupler U3, an absorption circuit module, a synchronous rectification module and a fast charging protocol chip. The voltage withstanding requirement of the main control chip is reduced, the input voltage overvoltage protection function is added, the ultra-wide voltage range can be output, the output voltage requirements of all fast charging power sources are met, and therefore the cost of the main control chip is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a switching power supply system and a control chip. Background Art

[0002] Since the flyback ACDC structure has the advantages of simple control and easy adjustment of output voltage, it is widely used in small and medium power power adapter applications. At present, most fast charging power supplies with a power of less than 100W use flyback ACDC architecture switching power supplies. PD fast charging power supplies need to dynamically adjust the output voltage according to the fast charging protocol of the terminal device. For example, the current output voltage is mostly 3.3V-20V, but the latest PD fast charging protocol output voltage range is increased to 3.3V-48V. Since the power supply of the control chip of the flyback switching power supply is supplied by the auxiliary winding of the transformer, its voltage is in direct proportion to the output voltage of the transformer turns ratio, so the power supply voltage of the control chip has the same change rate as the output voltage. For example, when the output voltage is 3.3V, the corresponding minimum voltage of the control chip power supply VCC is 12V. When the output voltage changes to 20V, the voltage of the chip power supply VCC is 72.7V. If the PD voltage output of 3.3V-20V is to be met, the withstand voltage of the control chip VCC must be greater than 72.7V. Similarly, if the PD voltage output of 3.3V-48V is to be met, the withstand voltage of the control chip VCC must be greater than 174.5V. The use of a high-voltage BCD process for the chip will significantly increase the chip cost. In order to reduce costs, most of the main control chips in the existing technology use dedicated withstand voltage chips to match various output voltage specifications. For example, a fast charging power supply with a maximum output voltage of 12V uses a 50V withstand voltage main control chip, and a fast charging voltage of up to 20V uses a 100V withstand voltage main control chip. This achieves cost optimization, but it requires the design of multiple main control chips, and it cannot meet the needs of higher output voltages. As a result, the main control chip of the fast charging power supply is costly and has a narrow scope of application.

[0003] At present, when the fast charging power supply adopts forward power supply, there are two problems with the forward power supply. First, the auxiliary winding cannot feedback the output voltage value, and the output voltage cannot be detected for output short circuit and overvoltage protection. Second, the power supply of the main drive chip cannot be guaranteed when the load is light. The reason is that when the auxiliary winding is connected in a flyback manner, the auxiliary winding and the secondary output winding are in a load parallel relationship. When the chip power supply voltage is reduced, the switch drive can be increased to increase it, which will not affect the output voltage. When the auxiliary winding is changed to a forward connection, the auxiliary winding and the primary winding are at the power supply end, that is, increasing the auxiliary winding power supply will also increase the output winding power supply. Excessive power supply of the forward auxiliary winding will cause the output voltage to be high. To solve this problem, the existing technology, such as patents CN113258784B and CN218449865U, not only adopts forward energy storage, but also adds a BOOST-like structure of flyback energy storage to improve the power supply capacity of the main control chip. It can be seen that this solution requires at least adding capacitors and a switch tube or diode to achieve, but this increases system cost and circuit board space without much beneficial effect. Summary of the invention

[0004] In order to overcome the shortcomings of the prior art, the present invention provides a switching power supply system and a control chip, which reduces the voltage resistance requirements of the main control chip, increases the input voltage overvoltage protection function, can output an ultra-wide voltage range, and meet the output voltage requirements of all fast charging power sources, thereby reducing the cost of the main control chip.

[0005] In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions: A switching power supply system and a control chip, including a fast charging power supply system, the fast charging power supply system including a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a resistor Rcs, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a transformer T1, a main controller chip U5, a voltage-stabilized power supply U4, an optical coupler U3, an absorption circuit module, a synchronous rectification module and a fast charging protocol chip; the primary winding Lp end of the transformer T1 is respectively connected to the negative end of the diode D1, the negative end of the diode D2, and the capacitor C1. The positive terminal of the diode D1 is connected to the negative terminal of the diode D3, the positive terminal of the diode D2 is connected to the negative terminal of the diode D4, the other end of the resistor R1 is respectively connected to the VCC pin of the main controller chip U5, the negative terminal of the diode D5 and one end of the capacitor C3, the positive terminal of the diode D5 is respectively connected to the auxiliary winding Laux of the transformer T1 and one end of the resistor R2, the other end of the resistor R2 is connected to the INV pin of the main controller chip U5, the FB pin of the main controller chip U5 is respectively connected to one end of the capacitor C2 and the output positive terminal of the optocoupler U3, the CS pin of the main controller chip U5 ... the negative terminal of the diode D4, the positive terminal of the diode D5 and the negative terminal of the diode D5 are respectively connected to the VCC pin of the main controller chip U5, the negative terminal of the diode D5 and the negative terminal of the diode D4, the positive terminal of the diode D5 and the negative terminal of the diode D5 are respectively connected to the VCC pin of the main controller chip U5, the negative terminal of the diode D5 and the negative terminal of the diode D4, the positive terminal of the diode D5 and the negative terminal of the diode D4 The GND pin of the main controller chip U5 is connected to one end of the resistor Rcs and one end of the switch N1, and the GND pin of the main controller chip U5 is respectively connected to the other end of the capacitor C5, the other end of the capacitor C2, the other end of the resistor Rcs, the other end of the capacitor C1, the positive end of the diode D3, the positive end of the diode D4 and the auxiliary winding Laux of the transformer T1. The auxiliary winding Laux of the transformer T1 and the primary winding Lp are the same end; the secondary output winding Ls of the transformer T1 is respectively connected to one end of the capacitor C4, one end of the resistor 5, one end of the resistor 7 and the fast charging protocol chip, and the other end of the resistor 7 is connected to the positive input terminal of the optocoupler U3. The voltage-regulated power supply U4 is respectively connected to the negative input terminal of the optocoupler U3. The positive terminal of the synchronous rectification circuit module is connected to the other end of the capacitor C5, and the secondary output winding Ls of the transformer T1 is respectively connected to the negative terminal of the diode D7 and the other end of the switch N2; the withstand voltage requirement of the main control chip is reduced, and the input voltage overvoltage protection function is increased, so as to output an ultra-wide voltage range and meet the output voltage requirements of all fast charging power sources, thereby reducing the cost of the main control chip.

[0006] Furthermore, the output voltage is detected by detecting the current flowing through the resistor R2, and at the same time, the INV pin of the main control chip U5 performs valley bottom detection of the primary winding.

[0007] Furthermore, when the output load is large, if the VOUT voltage is low, the voltage at the FB pin of the main control chip will increase under the action of the voltage-stabilized power supply U4, the optocoupler U3 and the pull-up resistor at the FB pin of the main control chip; if the VOUT voltage is high, the voltage at the FB pin of the main control chip will decrease under the action of the voltage-stabilized power supply U4, the optocoupler U3 and the pull-up resistor at the FB pin of the main control chip; when the load becomes lighter, the duration of closing the switch becomes longer, resulting in excessive power loss of the VCC capacitor of the main control chip; when there is no external load at the output end, the output energy storage capacitor C4 supplies power to the voltage-stabilized power supply U4, the voltage-dividing resistor R5, the voltage-dividing resistor R6 and the fast charging protocol chip.

[0008] Furthermore, the main controller chip U5 includes: a main controller, an output voltage detection module, a short-circuit overvoltage protection module, a power management module, a transistor P1, a resistor Rup and a resistor Rup1. The power management module is respectively connected to the main controller, the output voltage detection module, the short-circuit overvoltage protection module, the source end of the transistor P1, one end of the resistor Rup and the gate end of the transistor P1, the drain end of the transistor P1 is connected to one end of the resistor Rup1, the short-circuit overvoltage protection module is respectively connected to the output voltage detection module, the power management module and the main controller, the INV pin end of the main controller chip U5 is respectively connected to the output voltage detection module and the main controller, the power management module is respectively connected to the VCC pin end of the main controller chip U5 and the GND pin end of the main controller chip U5, the FB pin end of the main controller chip U5 is respectively connected to the other end of the resistor Rup, the other end of the resistor Rup1 and the main controller, the CS pin end of the main controller chip U5 is connected to the main controller, and the DRV pin end of the main controller chip U5 is connected to the main controller.

[0009] Furthermore, the power management module provides voltage and bias current for each module and manages the power consumption of all circuits when lightly loaded. Except for the functions required by the detection circuit at the FB pin of the main controller chip U5, the remaining circuits are turned off to save chip power consumption when lightly loaded. At the same time, by turning off the transistor P1, the Rup1 resistor is disconnected, the pull-up resistor at the FB pin is increased, and the power consumption at the FB pin is reduced.

[0010] Optionally, the transistor P1 and the resistor Rup1 may be designed with multiple groups of disconnectable resistors as required, and the resistors may be disconnected one by one as required to gradually reduce the pull-up current at the FB pin.

[0011] Furthermore, the output voltage detection module pulls the voltage of the INV pin of the main controller chip U5 to a set voltage value, and determines the voltage value of the auxiliary winding through the current flowing through the INV pin of the main controller chip U5 and the resistor R2, thereby realizing output voltage detection.

[0012] Furthermore, the output voltage detection module performs short-circuit overvoltage judgment on the current at the INV pin of the main controller chip U5: when the current at the INV pin of the main controller chip U5 is less than the set value, it is judged as an output short circuit; when the current at the INV pin of the main controller chip U5 is greater than the set value, it is judged as an output overvoltage.

[0013] Optionally, since the auxiliary winding voltage at the INV pin of the main controller chip U5 is in a turns ratio relationship with the input voltage of the primary winding, the high-level voltage at the INV pin of the main controller chip U5 is detected by the voltage detection module to determine whether the input voltage is undervoltage or overvoltage, or the voltage at the VCC pin of the main controller chip U5 is detected by the power management module. If there is overvoltage, overvoltage protection is performed.

[0014] Furthermore, the output voltage detection module includes a transistor P1, a transistor P2, a resistor R11, a comparator U11, a comparator U12 and a transistor N11. The transistors P1 and P2 are connected in a current mirror manner, and the current of P1 is mirrored to the output of the transistor P2. The gate and drain of the transistor P1 are connected, and then connected to the gate of the transistor P2. The internal power supply VDD terminal is respectively connected to the source terminal of the transistor P1 and the source terminal of P2. The drain output of the transistor P2 is connected to the R11 resistor and the positive input terminals of the comparators U11 and U12, and the negative input terminals of the comparators U11 and U12 are respectively connected to an internal reference voltage Vref1 and Vref2.

[0015] Furthermore, comparator U11 and comparator U12 output overvoltage signal and short circuit signal to the main controller respectively. Transistor N11 is a detection switch tube controlled by a Vt pulse signal. When it is detected that the auxiliary winding outputs a negative voltage, a pulse signal is output at the Vt terminal within a set time. This signal causes the source of transistor N11, i.e., the INV pin, to be pulled to a set voltage.

[0016] Furthermore, the voltage drop of resistor R2 is the negative voltage value of the auxiliary winding, which is proportional to the output voltage. The current of resistor R2 reflects the output voltage value, and the current flows from the P1 transistor to the N11 transistor, and then from the INV port to the resistor R2.

[0017] Furthermore, a switching cycle waveform of the main switch tube Drain end, the auxiliary winding AUX end and the chip INV end, when the main switch tube N1 is turned on at time t0, the Drain end voltage is pulled low, and the input voltage VIN is applied to the primary winding Lp of the transformer T1. Since the auxiliary winding is connected in a forward-excitation method, the auxiliary winding AUX outputs a high-level voltage at this time, and the voltage charges the capacitor at the VCC pin end of the main controller chip U5 through the diode D5. After charging is completed, the VCC voltage will be in a proportional relationship with the input voltage VIN in turns ratio; when the switch tube N1 is turned off, the Drain end voltage increases, and the secondary output winding outputs a positive voltage, and the primary winding and the auxiliary winding both output negative voltages.

[0018] Furthermore, during the Tdem time, when the Vt signal is pulled high, transistor N11 supplies power to the INV pin of the main controller chip U5 through transistor P1, so that I*R2=Vaux, where Vaux is the voltage value of the auxiliary winding at this time and is proportional to the output voltage. The current I is mirrored to the resistor R11 through transistors P1 and P2 and converted into a voltage value, which is then compared with the internal reference voltage.

[0019] Furthermore, the main controller will detect the voltage value of the FB pin of the main controller chip U5 in real time. When the voltage of the FB pin of the main controller chip U5 is lower than the set value Vrfb1, the output is a no-switch state flag and transmitted to the power management module, and the remaining modules except the FB detection module are controlled to be turned off. At the same time, the transistor P1 is controlled to be turned off, thereby reducing the power consumption of the pull-up resistor at the FB pin of the main controller chip U5. Since the pull-up current at the FB pin of the main controller chip U5 is reduced, the voltage at the FB pin of the main controller chip U5 will drop by a certain value, and the chip will enter a low power consumption state; when the load increases, the voltage at the FB pin will rise again, and when it rises to a set threshold Vrfb2, the main controller resets the no-switch state flag, and the power management module resumes the normal working mode, and the transistor P1 is turned on. At this time, the voltage at the FB pin is pulled up by a step, and the chip enters a normal power consumption state.

[0020] The output voltage detection module includes a transistor P1, a transistor P2, a resistor R11, a comparator U11, a comparator U12 and a transistor N11. The source end of the transistor P1, the source end of the transistor P2, the 1-pin end of the comparator U11 and the 3-pin end of the comparator U12 are connected to the VDD end of the power supply, the gate end of the transistor P1 is connected to the gate end of the transistor P2, the gate end of the transistor P1 is connected to the drain end of the transistor N11, the source end of the transistor N11 is connected to one end of the resistor R12, the other end of the resistor R12 is connected to the INV pin end, the gate end of the transistor P2 is respectively connected to one end of the resistor R11, the positive input pin end of the comparator U11 and the positive input pin end of the comparator U12, the gate end of the transistor N11, the other end of the resistor R11, the 2-pin end of the comparator U11 and the 4-pin end of the comparator U12 are grounded, and the output end of the comparator U11 and the output end of the comparator U12 are grounded and connected to the short-circuit overvoltage protection module.

[0021] The beneficial effects of the present application are: it is possible to reduce the voltage resistance requirement of the main control chip without increasing the system cost, thereby reducing the cost of the main control chip. The main control chip and the corresponding power supply system of the present invention can realize all the functions of the existing fast charging power supply, and add the input voltage overvoltage protection function, and can output an ultra-wide voltage range. A low-cost control chip can meet the output voltage requirements of all fast charging power supplies.

[0022] By adopting the auxiliary winding connection method of forward power supply, the auxiliary winding output is opposite to the secondary output winding output. When the output voltage of the secondary output winding is close to the output voltage, the auxiliary winding output is a negative voltage, but the absolute value of the voltage is still proportional to the winding turns ratio. Therefore, detecting the negative voltage can also detect the output voltage.

[0023] The present invention adjusts the polarity of the auxiliary winding Laux of the transformer T1, and the same-name end of the auxiliary winding is changed, and the existing flyback auxiliary winding power supply is changed to a forward auxiliary winding power supply. At the same time, compared with the prior art, the present invention also saves the R3 resistor. The main change is to adjust the function of the main control chip U5 to make it suitable for the forward power supply solution, so that the INV pin end of the main control chip can detect the voltage and the valley bottom detection function of the primary winding, while the prior art uses the R2 and R3 resistors to divide the output voltage.

[0024] This control method can greatly reduce the power consumption of the main control chip when there is no switching waveform under light load, avoid excessive power loss of the chip VCC capacitor, and enable the switching power supply of the forward power supply mode to work normally under light load. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0026] Figure 1 is a circuit diagram of a switching power supply system of the present invention; Figure 2 is a circuit diagram of a prior art switching power supply system; Figure 3 It is a structural schematic diagram of the main control chip of the present invention; Figure 4 is a circuit diagram of an output voltage detection module of the present invention; Figure 5 is an output voltage detection signal waveform diagram of the present invention; Figure 6 It is a schematic diagram of the power consumption management state of the present invention. DETAILED DESCRIPTION

[0027] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0028] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the following embodiments and features in the embodiments can be combined with each other without conflict. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work belong to the scope of protection of the present invention.

[0029] Embodiment 1: like Figure 3As shown, a switching power supply system and a control chip include a fast charging power supply system, the fast charging power supply system includes a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a resistor Rcs, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a transformer T1, a main controller chip U5, a voltage-stabilizing power supply U4, an optocoupler U3, an absorption circuit module, a synchronous rectification module and a fast charging protocol chip; the primary winding Lp end of the transformer T1 is respectively connected to the negative end of the diode D1, the negative end of the diode D2, and the capacitor One end of C1, one end of resistor R1 are connected to the absorption circuit module, the positive end of diode D1 is connected to the negative end of diode D3, the positive end of diode D2 is connected to the negative end of diode D4, the other end of resistor R1 is respectively connected to the VCC pin of main controller chip U5, the negative end of diode D5 and one end of capacitor C3, the positive end of diode D5 is respectively connected to the auxiliary winding Laux of transformer T1 and one end of resistor R2, the auxiliary winding Laux of transformer T1 and the primary winding Lp are the same end, the other end of resistor R2 is connected to the INV pin of main controller chip U5, the FB pin of main controller chip U5 is respectively connected to one end of capacitor C2. The CS pin of the main controller chip U5 is connected to one end of the resistor Rcs and one end of the switch N1, and the GND pin of the main controller chip U5 is respectively connected to the other end of the capacitor C5, the other end of the capacitor C2, the other end of the resistor Rcs, the other end of the capacitor C1, the positive end of the diode D3, the positive end of the diode D4 and the auxiliary winding Laux of the transformer T1; the secondary output winding Ls of the transformer T1 is respectively connected to one end of the capacitor C4, one end of the resistor 5, one end of the resistor 7 and the fast charging protocol chip, the other end of the resistor 7 is connected to the input positive terminal of the optocoupler U3, and the voltage-regulated power supply U4 is respectively connected to the input negative electrode of the optocoupler U3. The positive terminal of the synchronous rectification circuit module is connected to the other end of the capacitor C5, and the secondary output winding Ls of the transformer T1 is respectively connected to the negative terminal of the diode D7 and the other end of the switch N2; the withstand voltage requirement of the main control chip is reduced, and the input voltage overvoltage protection function is increased, so as to output an ultra-wide voltage range and meet the output voltage requirements of all fast charging power sources, thereby reducing the cost of the main control chip.

[0030] like Figure 2 , 3As shown, the present invention adjusts the polarity of the auxiliary winding Laux of the transformer T1, and the same-name end of the auxiliary winding is changed, and the existing flyback auxiliary winding power supply is changed to a forward auxiliary winding power supply. At the same time, compared with the prior art, the present invention also saves the R3 resistor. The main change is to adjust the function of the main control chip U5 to make it suitable for the forward power supply solution, so that the INV pin end of the main control chip is used for voltage detection and the valley bottom detection function of the primary winding is realized, while the prior art uses the R2 and R3 resistors to divide the output voltage.

[0031] The present invention needs to adjust the detection circuit, and detects the size of the output voltage by detecting the current flowing through the R2 resistor. At the same time, the INV pin end of the main control chip U5 also has an oscillating waveform of the primary winding, and the valley detection function of the primary winding can be performed. As shown in Figure 3, when the output load is large, the VOUT voltage is low. Under the action of the pull-up resistor at the FB pin end of the voltage-stabilized power supply U4, the optical coupler U3 and the main control chip, the FB pin end voltage of the main control chip will increase. On the contrary, when the VOUT voltage is high, under the action of the pull-up resistor at the FB pin end of the voltage-stabilized power supply U4, the optical coupler U3 and the main control chip, the FB pin end voltage of the main control chip will decrease. Usually, when the FB pin end voltage of the main control chip is lower than a certain value, the system will enter the interval pulse working mode, that is, the switch is turned on for a period of time and then the switch is turned off for a period of time. When the load becomes lighter, the duration of turning off the switch becomes longer, which will cause the VCC capacitor of the main control chip to lose power too much. When there is no external load at the output end, the system is at its lightest. At this time, the output energy storage capacitor C4 supplies power to the voltage-stabilized power supply U4, the voltage-dividing resistor R5, the voltage-dividing resistor R6 and the fast-charging protocol chip.

[0032] The capacity of the energy storage capacitor C4 is related to the output power. Taking the 65W solution as an example, the output energy storage capacitor C4 has a capacity of 470uF*2, and the VCC capacitor of the main control chip is generally 4.7uF. The output energy storage capacitor is 200 times the VCC capacitor of the main control chip. The output voltage light load ripple is generally above 100mV, which is set to 100mV. That is, after the output voltage drops by 100mV, the output switch of the main control chip will be started to raise the output voltage. If the VCC of the main control chip is allowed to drop by 2V, from I*t=C*ΔV, the output end C*ΔV=470uF*2*0.1V=94u, and the chip VCC end C*ΔV=4.7uF*2V=9.4u, it can be known that the VCC power consumption of the main control chip needs to be 1 / 10 of the power consumption of the output end during the same shutdown time, that is, the power consumption of the main control chip needs to be controlled within 0.1mA when lightly loaded, so that the normal operation of the main control chip can be guaranteed. To achieve this goal, it is necessary to perform dynamic power management on the main control chip, that is, the chip consumes more power when the switch is working, and consumes less power when the chip is in light load standby.

[0033] like Figure 1As shown, the main controller chip U5 includes: a main controller, an output voltage detection module, a short-circuit overvoltage protection module, a power management module, a transistor P1, a resistor Rup and a resistor Rup1. The power management module is respectively connected to the main controller, the output voltage detection module, the short-circuit overvoltage protection module, the source end of the transistor P1, one end of the resistor Rup and the gate end of the transistor P1, the drain end of the transistor P1 is connected to one end of the resistor Rup1, the short-circuit overvoltage protection module is respectively connected to the output voltage detection module, the power management module and the main controller, the INV pin end of the main controller chip U5 is respectively connected to the output voltage detection module and the main controller, the power management module is respectively connected to the VCC pin end of the main controller chip U5 and the GND pin end of the main controller chip U5, the FB pin end of the main controller chip U5 is respectively connected to the other end of the resistor Rup, the other end of the resistor Rup1 and the main controller, the CS pin end of the main controller chip U5 is connected to the main controller, and the DRV pin end of the main controller chip U5 is connected to the main controller.

[0034] The power management module is responsible for providing voltage and bias current for each module, and managing the power consumption of all circuits when lightly loaded. Except for the related circuit functions required by the detection circuit at the FB pin of the main controller chip U5, the rest of the circuits are turned off, which greatly saves the chip power consumption when lightly loaded. At the same time, by turning off the transistor P1, the Rup1 resistor is disconnected, the pull-up resistor at the FB pin is increased, and the power consumption at the FB pin is reduced. It should be noted that, as shown in 1, only one group of transistor P1 and resistor Rup1 is shown. In fact, multiple groups of disconnectable resistors can be designed as needed, and the resistors can be disconnected one by one as needed to gradually reduce the pull-up current at the FB pin.

[0035] By adopting the auxiliary winding connection method of forward power supply, the output of the auxiliary winding is opposite to the output of the secondary output winding. When the output voltage of the secondary output winding is close to the output voltage, the output of the auxiliary winding is a negative voltage, but the absolute value of the voltage is still proportional to the winding turns ratio. Therefore, detecting the negative voltage can also detect the output voltage. The voltage detection module pulls the INV pin to a set voltage value, and by testing the current flowing through the INV pin and the R2 resistor, the voltage value of the auxiliary winding can be calculated to detect the output voltage. After the voltage detection module detects the current at the INV pin, it converts it into a voltage value and outputs it to the short-circuit and overvoltage protection module. The current at the INV pin is judged. When the current at the INV pin is less than the set value, the output is considered to be short-circuited. When the current at the INV pin is greater than the set value, the output is considered to be overvoltage. Since the auxiliary winding voltage at the INV pin is in a turns ratio relationship with the input voltage of the primary winding, the voltage detection module can also be used to detect the high-level voltage at the INV pin to determine whether the input voltage is undervoltage or overvoltage, or the power management module can be used to detect the voltage at the VCC pin of the chip. If it is overvoltage, overvoltage protection occurs. The above short circuit, undervoltage and overvoltage will trigger the protection, shut down the main control chip, and turn it on again when the voltage meets the requirements.

[0036] like Figure 4 As shown, the output voltage detection module includes a transistor P1, a transistor P2, a resistor R11, a comparator U11, a comparator U12 and a transistor N11. The source end of the transistor P1, the source end of the transistor P2, the 1-pin end of the comparator U11 and the 3-pin end of the comparator U12 are connected to the VDD end of the power supply, the gate end of the transistor P1 is connected to the gate end of the transistor P2, the gate end of the transistor P1 is connected to the drain end of the transistor N11, the source end of the transistor N11 is connected to one end of the resistor R12, the other end of the resistor R12 is connected to the INV pin end, the gate end of the transistor P2 is respectively connected to one end of the resistor R11, the positive input pin end of the comparator U11 and the positive input pin end of the comparator U12, the gate end of the transistor N11, the other end of the resistor R11, the 2-pin end of the comparator U11 and the 4-pin end of the comparator U12 are grounded, and the output end of the comparator U11 and the output end of the comparator U12 are grounded and connected to the short-circuit overvoltage protection module.

[0037] It should be noted that the gate input of transistor N11 is a Vtc signal, and a resistor R12 is added to the source of transistor N11 to protect transistor N11 and prevent INV voltage spikes from damaging transistor N11. The negative input terminals of comparators U11 and U12 are connected to internal reference voltages Vref1 and Vref2, respectively. Comparators U11 and U12 output overvoltage signals and short-circuit signals to the main controller, respectively. Transistor N11 is a detection switch tube controlled by a Vt pulse signal. When a negative voltage is detected output by the auxiliary winding, a pulse signal is output at the Vt terminal within a set time. This signal causes the source of transistor N11, i.e., the INV pin, to be pulled to a set voltage, such as 0V. Figure 3 As shown in the figure, the voltage drop of resistor R2 is the negative voltage value of the auxiliary winding, which is proportional to the output voltage. The current of resistor R2 reflects the output voltage value, and its current flows from transistor P1 to transistor N11, and then from the INV port to resistor R2.

[0038] like Figure 5 As shown, the output voltage detection signal is performed: a switching cycle waveform of the main switch tube Drain terminal, the auxiliary winding AUX terminal and the chip INV terminal. When the main switch tube N1 is turned on at time t0, the voltage at the Drain terminal is pulled low, and the input voltage VIN is applied to the primary winding Lp of the transformer T1. Since the auxiliary winding is connected in a forward-pulse method, the auxiliary winding AUX outputs a high-level voltage at this time. This voltage charges the VCC capacitor of the chip through the D5 diode. After charging is completed, the VCC voltage will be in a proportional relationship with the input voltage VIN. When the switch tube N1 is turned off, the voltage at the Drain terminal increases. At this time, the secondary output winding outputs a positive voltage, and the primary winding and the auxiliary winding both output a negative voltage. It should be noted that the negative voltage output by the primary winding means that the voltage at the Drain terminal is higher than the input voltage VIN. As shown Figure 5 As shown in the Tdem time period, during the Tdem time, when the Vt signal is pulled high, the transistor N11 will supply power to the INV terminal through the transistor P1, so that I*R2=Vaux, where Vaux is the voltage value of the auxiliary winding at this time, which is proportional to the output voltage. The current I is mirrored to the resistor R11 through the transistor P1 and the transistor P2, and converted into a voltage value, which is then compared with the internal reference voltage.

[0039] like Figure 6As shown, the output voltage detection signal is performed: the main controller will detect the voltage value of the FB pin of the main controller chip U5 in real time. When the voltage of the FB pin of the main controller chip U5 is lower than the set value Vrfb1, the no-switch state flag is output and output to the power management module, and the remaining modules except the FB detection module are controlled to be turned off. At the same time, the transistor P1 is controlled to be turned off to reduce the power consumption of the pull-up resistor at the FB pin. Since the pull-up current at the FB pin is reduced, the voltage at the FB pin will drop by a certain value. At this time, the chip enters a low-power state. When the load increases, the voltage at the FB pin will rise again. When it rises to a set threshold Vrfb2, the main controller resets the no-switch state flag, and the power management module resumes the normal working mode. The transistor P1 is turned on. At this time, the voltage at the FB pin is pulled up by a step, and the chip enters a normal power consumption state. The use of this control method can greatly reduce the power consumption of the main control chip when there is a light load and no switching waveform, avoid excessive power loss of the chip VCC capacitor, and enable the switching power supply of the forward power supply method to work normally under light load.

[0040] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0041] The terms "including" and "having" and any variations thereof in the specification of the present application and the above-mentioned drawings are intended to cover non-exclusive inclusions. For example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units that are not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0042] The units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. In addition, each functional unit in each embodiment of the present application may be integrated into a processing unit, or each unit may exist physically separately, or two or more units may be integrated into one unit. The above-mentioned integrated units may be implemented in the form of hardware or in the form of software functional units.

[0043] As described above, the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims

1. A switching power supply system and control chip, It is characterized in that The fast charging power supply system includes a diode D1, a diode D2, a diode D3, a diode D4, a diode D5, a diode D6, a diode D7, a resistor Rcs, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a transformer T1, a main controller chip U5, a voltage-stabilized power supply U4, an optocoupler U3, an absorption circuit module, a synchronous rectification module and a fast charging protocol chip; the primary winding Lp end of the transformer T1 is respectively connected to the negative end of the diode D1, the negative end of the diode D2, and the capacitor C 1, one end of the resistor R1 is connected to the absorption circuit module, the positive end of the diode D1 is connected to the negative end of the diode D3, the positive end of the diode D2 is connected to the negative end of the diode D4, the other end of the resistor R1 is respectively connected to the VCC pin end of the main controller chip U5, the negative end of the diode D5 and one end of the capacitor C3, the positive end of the diode D5 is respectively connected to the auxiliary winding Laux end of the transformer T1 and one end of the resistor R2, the other end of the resistor R2 is connected to the INV pin end of the main controller chip U5, the FB pin end of the main controller chip U5 is respectively connected to one end of the capacitor C2 The CS pin of the main controller chip U5 is connected to one end of the resistor Rcs and one end of the switch N1, and the GND pin of the main controller chip U5 is respectively connected to the other end of the capacitor C5, the other end of the capacitor C2, the other end of the resistor Rcs, the other end of the capacitor C1, the positive end of the diode D3, the positive end of the diode D4 and the auxiliary winding Laux of the transformer T1, and the auxiliary winding Laux of the transformer T1 is the same as the primary winding Lp; the secondary output winding Ls of the transformer T1 is respectively connected to one end of the capacitor C4, one end of the resistor 5, one end of the resistor 7 and The fast charging protocol chip is connected, the other end of the resistor 7 is connected to the input positive terminal of the optocoupler U3, the voltage-regulated power supply U4 is respectively connected to the input negative terminal of the optocoupler U3, the other end of the resistor 5, one end of the resistor 6 and the fast charging protocol chip, the synchronous rectification circuit module is respectively connected to the output negative terminal of the optocoupler U3, the other end of the resistor 6, the other end of the capacitor C4, one end of the capacitor C5, the positive terminal of the diode D7, one end of the switch N2 and the fast charging protocol chip, the positive terminal of the synchronous rectification circuit module is connected to the other end of the capacitor C5, and the secondary output winding Ls of the transformer T1 is respectively connected to the negative terminal of the diode D7 and the other end of the switch N2.

2. The switching power supply system and control chip according to claim 1, It is characterized in that When the output load is large, if the VOUT voltage is low, under the action of the voltage-stabilized power supply U4, the optocoupler U3 and the pull-up resistor at the FB pin of the main control chip, the voltage at the FB pin of the main control chip will increase; if the VOUT voltage is high, under the action of the voltage-stabilized power supply U4, the optocoupler U3 and the pull-up resistor at the FB pin of the main control chip, the voltage at the FB pin of the main control chip will decrease; when the load becomes lighter, the duration of closing the switch becomes longer, resulting in excessive power loss of the VCC capacitor of the main control chip; when there is no external load at the output end, the output energy storage capacitor C4 supplies power to the voltage-stabilized power supply U4, the voltage-dividing resistor R5, the voltage-dividing resistor R6 and the fast charging protocol chip.

3. The switching power supply system and control chip according to claim 1, It is characterized in that The main controller chip U5 includes: a main controller, an output voltage detection module, a short-circuit overvoltage protection module, a power management module, a transistor P1, a resistor Rup and a resistor Rup1. The power management module is respectively connected to the main controller, the output voltage detection module, the short-circuit overvoltage protection module, the source end of the transistor P1, one end of the resistor Rup and the gate end of the transistor P1, the drain end of the transistor P1 is connected to one end of the resistor Rup1, the short-circuit overvoltage protection module is respectively connected to the output voltage detection module, the power management module and the main controller, the INV pin end of the main controller chip U5 is respectively connected to the output voltage detection module and the main controller, the power management module is respectively connected to the VCC pin end of the main controller chip U5 and the GND pin end of the main controller chip U5, the FB pin end of the main controller chip U5 is respectively connected to the other end of the resistor Rup, the other end of the resistor Rup1 and the main controller, the CS pin end of the main controller chip U5 is connected to the main controller, and the DRV pin end of the main controller chip U5 is connected to the main controller.

4. The switching power supply system and control chip according to claim 3, It is characterized in that The power management module provides voltage and bias current for each module, and manages the power consumption of all circuits when lightly loaded. Except for the functions required by the detection circuit at the FB pin end of the main controller chip U5, the remaining circuits are turned off to save chip power consumption when lightly loaded. At the same time, by turning off the transistor P1, the Rup1 resistor is disconnected, the pull-up resistor at the FB pin end is increased, and the power consumption at the FB pin end is reduced.

5. The switching power supply system and control chip according to claim 3, It is characterized in that The output voltage detection module pulls the voltage of the INV pin of the main controller chip U5 to a set voltage value, and determines the voltage value of the auxiliary winding through the current flowing through the INV pin of the main controller chip U5 and the R2 resistor, thereby realizing output voltage detection.

6. The switching power supply system and control chip according to claim 3, It is characterized in that The output voltage detection module performs short-circuit overvoltage judgment on the current at the INV pin end of the main controller chip U5: when the current at the INV pin end of the main controller chip U5 is less than the set value, it is judged as an output short circuit; when the current at the INV pin end of the main controller chip U5 is greater than the set value, it is judged as an output overvoltage.

7. The switching power supply system and control chip according to claim 3, It is characterized in that The output voltage detection module includes a transistor P1, a transistor P2, a resistor R11, a comparator U11, a comparator U12 and a transistor N11. The source end of the transistor P1, the source end of the transistor P2, the 1-pin end of the comparator U11 and the 3-pin end of the comparator U12 are connected to the VDD end of the power supply, the gate end of the transistor P1 is connected to the gate end of the transistor P2, the gate end of the transistor P1 is connected to the drain end of the transistor N11, the source end of the transistor N11 is connected to one end of the resistor R12, the other end of the resistor R12 is connected to the INV pin end, the gate end of the transistor P2 is respectively connected to one end of the resistor R11, the positive input pin end of the comparator U11 and the positive input pin end of the comparator U12, the gate end of the transistor N11, the other end of the resistor R11, the 2-pin end of the comparator U11 and the 4-pin end of the comparator U12 are grounded, and the output end of the comparator U11 and the output end of the comparator U12 are grounded and connected to the short-circuit overvoltage protection module.

8. The switching power supply system and control chip according to claim 7, It is characterized in that The comparator U11 and the comparator U12 output an overvoltage signal and a short-circuit signal to the main controller respectively. The transistor N11 is controlled by the Vt pulse signal. When it is detected that the auxiliary winding outputs a negative voltage, a pulse signal is output at the Vt terminal within a set time. This signal causes the source of the transistor N11, i.e., the INV pin, to be pulled to a set voltage.

9. The switching power supply system and control chip according to claim 1, It is characterized in that A switching cycle waveform of the main switch tube Drain end, the auxiliary winding AUX end and the chip INV end. When the main switch tube N1 is turned on at time t0, the voltage at the Drain end is pulled down, and the input voltage VIN is applied to the primary winding Lp of the transformer T1. Since the auxiliary winding is connected in a forward-excitation method, the auxiliary winding AUX outputs a high-level voltage at this time, and the voltage charges the capacitor at the VCC pin end of the main controller chip U5 through the diode D5. After charging, the VCC voltage will be in a proportional relationship with the input voltage VIN in turns ratio; when the switch tube N1 is turned off, the voltage at the Drain end increases, and the secondary output winding outputs a positive voltage, and the primary winding and the auxiliary winding both output negative voltages.

10. The switching power supply system and control chip according to claim 1, It is characterized in that The main controller will detect the voltage value of the FB pin of the main controller chip U5 in real time. When the voltage of the FB pin of the main controller chip U5 is lower than the set value Vrfb1, it will output a no-switch state flag and transmit it to the power management module, control the remaining modules except the FB pin detection module of the main controller chip U5 to be turned off, and control the transistor P1 to be turned off at the same time, reduce the power consumption of the pull-up resistor at the FB pin of the main controller chip U5. Since the pull-up current of the FB pin of the main controller chip U5 is reduced, the voltage at the FB pin of the main controller chip U5 will drop by a certain value, and the chip will enter a low power consumption state; when the load increases, the voltage at the FB pin will rise again, and when it rises to a set threshold Vrfb2, the main controller resets the no-switch state flag, the power management module resumes the normal working mode, and the transistor P1 is turned on. At this time, the voltage at the FB pin is pulled up by a step, and the chip enters a normal power consumption state.

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