A voltage conversion circuit and an isolated power supply system

Abstract

The present invention provides a voltage conversion circuit and an isolated power supply system. The voltage conversion circuit includes: a switching power supply chip, which includes a power MOS transistor and a driving circuit, and the driving circuit is adapted to drive the power MOS transistor to operate; it further includes: a driving circuit power supply unit, including a boosting unit, when the voltage output by the boosting unit has not reached the operating voltage of the driving circuit, the internal power supply of the switching power supply chip provides the operating voltage for the driving circuit; when the voltage output by the boosting unit reaches the operating voltage of the driving circuit, the voltage output by the boosting unit serves as the operating voltage of the driving circuit.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic circuits, and particularly to a voltage conversion circuit and an isolated power supply system. Background Art

[0002] Switching power supplies are known as energy-efficient power supplies, representing the development direction of regulated power supplies. They have now become the mainstream products of regulated power supplies and have been widely applied in fields such as electric power, communication, transportation, and industrial control. In recent years, with the continuous development and improvement of power electronics technology and industrial manufacturing levels, various types and functions of switching power supply systems have emerged one after another, greatly expanding the technical selection space for users.

[0003] At present, for traditional non-isolated power supply systems, to increase the output power, a larger power MOS transistor is first required, and the insufficient internal voltage of the chip is the main factor restricting the drive. The traditional methods for increasing the internal power supply voltage of the chip mainly include the following two: one is to adopt a traditional self-powered structure, where the internal power supply of the chip is generated by the high-voltage input terminal of the chip to drive the power MOS transistor; the other is to make the output voltage pass through a winding with a turns ratio of 1:N, so as to obtain a higher voltage and feedback it to the inside of the chip to drive the power MOS transistor. However, in actual use, the efficiency of the first self-powered structure is relatively low, and the system loss is relatively large; while the second method adds a winding to the entire system, making the system relatively complex, the structure not concise enough, and the system assembly cost relatively high.

[0004] Therefore, a new voltage conversion circuit is needed. Summary of the Invention

[0005] The problem to be solved by the present invention is: for a non-isolated power supply system, to provide a new voltage conversion circuit, the voltage conversion circuit has a simple structure, low cost, and high working efficiency.

[0006] To solve the above problems, an embodiment of the present invention provides a voltage conversion circuit, including: a switching power supply chip, the switching power supply chip includes a power MOS transistor and a drive circuit, and the drive circuit is adapted to drive the power MOS transistor to work; the voltage conversion circuit further includes: a drive circuit power supply unit, including a boost unit, when the voltage output by the boost unit has not reached the working voltage of the drive circuit, the internal power supply of the switching power supply chip provides the working voltage for the drive circuit; when the voltage output by the boost unit reaches the working voltage of the drive circuit, the voltage output by the boost unit serves as the working voltage of the drive circuit.

[0007] Optionally, the switching power supply chip further includes: a chip power supply pin, a chip ground pin, and a chip auxiliary power supply pin.

[0008] Optionally, the driving circuit power supply unit further includes a buffer unit. The input end of the buffer unit is coupled to the chip power supply pin, and the output end of the buffer unit is coupled to the power input end of the driving circuit and the chip auxiliary power supply pin. When the voltage output by the boost unit has not reached the operating voltage of the driving circuit, the internal power supply of the switching power supply chip provides the operating voltage to the driving circuit through the buffer unit.

[0009] Optionally, the input end of the boost unit is coupled to the chip power supply pin, and the output end of the boost unit is coupled to the chip auxiliary power supply pin and the power input end of the driving circuit.

[0010] Optionally, the voltage conversion circuit further includes: an auxiliary power supply capacitor. The negative electrode of the auxiliary power supply capacitor is coupled to the chip power supply pin or the chip ground pin, and the positive electrode of the auxiliary power supply capacitor is coupled to the chip auxiliary power supply pin. The auxiliary power supply capacitor is adapted to store the charge generated on the chip auxiliary power supply pin.

[0011] Optionally, the auxiliary power supply capacitor is integrated inside the switching power supply chip or disposed outside the switching power supply chip.

[0012] Optionally, the switching power supply chip further includes: a control unit. The power supply end of the control unit is coupled to the chip power supply pin, and the first output end of the control unit is coupled to the input end of the driving circuit and is adapted to provide a first control signal to the driving circuit.

[0013] Optionally, the first control signal is a switching control signal.

[0014] Optionally, the buffer unit includes a diode.

[0015] Optionally, the buffer unit includes a first MOS transistor. The gate of the first MOS transistor is coupled to the second output end of the control unit to receive the second control signal input by the second output end. The source of the first MOS transistor is coupled to the chip power supply pin, and the drain of the first MOS transistor is coupled to the power input end of the driving circuit and the chip auxiliary power supply pin.

[0016] Optionally, the second control signal is used to control the switching of the first MOS transistor. When the voltage on the chip auxiliary power supply pin has not reached the operating voltage of the drive circuit, the second control signal controls the first MOS transistor to turn on, and the chip power supply pin provides the operating voltage to the drive circuit through the first MOS transistor; when the voltage on the chip auxiliary power supply pin reaches the operating voltage of the drive circuit, the second control signal controls the first MOS transistor to turn off, and the chip auxiliary power supply pin provides the operating voltage to the drive circuit.

[0017] Optionally, the boost unit includes a charge pump boost circuit.

[0018] Optionally, the drive circuit includes N NMOS transistors and M PMOS transistors; wherein, the gates of the N NMOS transistors and the M PMOS transistors are all coupled to the first output end of the control unit to input the first control signal; the drains of the N NMOS transistors and the M PMOS transistors are all coupled together as the output of the drive circuit and are coupled to the gate of the power MOS transistor; the sources of the N NMOS transistors are all coupled to the chip ground pin, and the sources of the M PMOS transistors are all coupled together as the power input terminal of the drive circuit, and the drive circuit power supply unit provides the operating voltage for it.

[0019] An embodiment of the present invention further provides a non-isolated power supply system, including: a rectification unit, an output inductor, a feedback diode, and a voltage conversion circuit as described in the foregoing embodiment; wherein, the input end of the rectification unit is coupled to an external AC power supply, and its output end is coupled to the high-voltage input pin of the switching power supply chip. The rectification unit is adapted to rectify the externally input alternating current into direct current and input the direct current into the high-voltage input pin; the input end of the output inductor is coupled to the chip ground pin of the switching power supply chip, and the output end of the output inductor is coupled to the output end of the non-isolated power supply system; the positive pole of the feedback diode is coupled to the output end of the non-isolated power supply system, and the negative pole of the feedback diode is coupled to the chip power supply pin, and is adapted to feedback the output voltage of the non-isolated power supply system to the chip power supply pin.

[0020] Optionally, the control unit further includes: a third output terminal coupled to the control signal input terminal of the boost unit, adapted to control the switch of the boost unit: when the voltage at the output terminal of the non-isolated power supply system is relatively high and the voltage of the chip power supply pin can meet the power supply requirement of the drive circuit, the third output terminal of the control unit outputs a third control signal to turn off the boost circuit, and the chip power supply pin supplies power to the drive circuit through the buffer unit of the switching power supply chip; when the voltage at the output terminal of the non-isolated power supply system is relatively low and the voltage of the chip power supply pin cannot meet the power supply requirement of the drive circuit, the third output terminal of the control unit outputs a third control signal to turn on the boost unit, and the output terminal of the boost unit supplies power to the drive circuit.

[0021] Optionally, the non-isolated power supply system further includes: an output capacitor, the positive electrode of the output capacitor is coupled to the output terminal of the non-isolated power supply system, and its negative electrode is coupled to the ground of the isolated power supply system; a chip power supply capacitor, the positive electrode of the chip power supply capacitor is coupled to the chip power supply pin, and its negative electrode is coupled to the chip ground pin; a freewheeling diode, the positive electrode of the freewheeling diode is coupled to the ground of the non-isolated power supply system, and its negative electrode is coupled to the positive electrode of the output inductor.

[0022] In summary, for the voltage conversion circuit provided by the embodiment of the present invention, when the chip power supply voltage is relatively low and cannot drive the power MOS transistor, the drive circuit power supply unit boosts the chip power supply voltage, and uses the boosted voltage to drive the power MOS transistor. The boosted drive voltage is generated by the internal power supply of the chip instead of being generated by external power supply, which is beneficial to reducing the loss of the switching power supply chip and has high conversion efficiency.

[0023] Further, the voltage conversion circuit provided by the embodiment of the present invention further includes an auxiliary power supply capacitor, which can help store the charge generated at the chip auxiliary power supply pin and improve the power supply capacity of the chip auxiliary power supply pin. And the auxiliary power supply capacitor can be arranged inside or outside the switching power supply chip, with a simple structure and low cost.

[0024] Further, the non-isolated power supply system provided by the embodiment of the present invention uses a feedback diode to feedback the voltage of the output terminal of the non-isolated power supply system to the chip power supply pin of the switching power supply chip, and determines whether to turn on the boost unit according to the magnitude of the voltage at the output terminal. The non-isolated power supply system has high voltage conversion efficiency, low system loss, and a simple structure. Description of the Drawings

[0025] Figure 1 is a schematic structural diagram of a voltage conversion circuit in an embodiment of the present invention;

[0026] Figure 2 In one embodiment of the present invention Figure 1 is a schematic framework diagram of a driving circuit power supply unit in a voltage conversion circuit;

[0027] Figure 3 is a schematic framework diagram of a driving circuit power supply unit in a voltage conversion circuit; Figure 2 is a schematic circuit diagram of the driving circuit power supply unit in the present invention;

[0028] Figure 4 In another embodiment of the present invention Figure 2 is a schematic circuit diagram of the driving circuit power supply unit in the present invention;

[0029] Figure 5 is a schematic circuit diagram of a driving circuit in one embodiment of the present invention; and

[0030] Figure 6 shows a schematic circuit diagram of a non-isolated power supply system according to one embodiment of the present invention. Detailed implementation manners

[0031] As described in the background art, for a traditional non-isolated power supply system with a self-powered structure, the efficiency is low and the system loss is large; while for a non-isolated power supply system with an additional winding having a coil turn ratio of 1:N, the peripheral system structure is complex and the system assembly cost is relatively high.

[0032] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] Figure 1 is a schematic structural diagram of a voltage conversion circuit in an embodiment of the present invention, Figure 2 is a schematic structural diagram of a driving circuit power supply unit 5 in one embodiment of the present invention. The following will be described with reference to Figure 1 and Figure 1 and Figure 2, the structure and working principle of the voltage conversion circuit are described in detail. The voltage conversion circuit 1A includes a switching power supply chip 1, and the switching power supply chip 1 includes a power MOS transistor 2 and a driving circuit 4. The driving circuit 4 is adapted to drive the power MOS transistor 2 to work. The voltage conversion circuit 1A further includes a driving circuit power supply unit 5, and the driving circuit power supply unit 5 includes a boosting unit 52. When the voltage output by the boosting unit 52 has not reached the working voltage of the driving circuit 4, the internal power supply of the switching power supply chip 1 provides the working voltage for the driving circuit 4. When the voltage output by the boosting unit 52 reaches the working voltage of the driving circuit 4, the voltage output by the boosting unit 52 serves as the working voltage of the driving circuit 4.

[0034] In one embodiment, the switching power supply chip 1 further includes: a chip power supply pin IO1, a chip ground pin GND1, and a chip auxiliary power supply pin IO2.

[0035] In one embodiment, the input terminal IO4 of the driving circuit power supply unit 5 is coupled to the chip power supply pin IO1, and the output terminal IO5 of the driving circuit power supply unit 5 is coupled to the chip auxiliary power supply pin IO2 and the power supply input terminal IO9 of the driving circuit.

[0036] In one embodiment, the voltage conversion circuit 1A further includes: an auxiliary power supply capacitor C1. The negative electrode of the auxiliary power supply capacitor C1 is coupled to the chip power supply pin IO1 or the chip ground pin GND1, and the positive electrode of the auxiliary power supply capacitor C1 is coupled to the chip auxiliary power supply pin IO2. The auxiliary power supply capacitor C1 is adapted to store the charge generated on the chip auxiliary power supply pin IO2.

[0037] In one embodiment, the auxiliary power supply capacitor C1 can be disposed outside the switching power supply chip 1, as Figure 1 shown. In other embodiments, the auxiliary power supply capacitor C1 can also be integrated inside the switching power supply chip 1.

[0038] In one embodiment, the switching power supply chip 1 further includes a control unit 3. The power supply terminal IO6 of the control unit 3 is coupled to the chip power supply pin IO1, and the first output terminal IO7 of the control unit 3 is coupled to the input terminal IO8 of the driving circuit 4 and is adapted to provide a first control signal K1 for the driving circuit 4. Specifically, the first control signal is a switching control signal. In one embodiment, the first control signal is a PWM signal. The structure and working principle of the control circuit are well-known technologies in the art and will not be described in detail herein. Those skilled in the art can understand that the structure of the control circuit should not be used to limit the scope claimed in the present application.

[0039] ReferenceFigure 2 In one embodiment, the driving circuit power supply unit 5 includes a buffer unit 51 and a boost unit 52, the input end IO51 of the buffer unit 51 and the input end IO53 of the boost unit 52 are coupled together to serve as the input end IO4 of the driving circuit power supply unit 5; the output end IO52 of the buffer unit 51 and the output end IO54 of the boost unit 52 are coupled together to serve as the output end IO5 of the driving circuit power supply unit 5. Figure 1 and Figure 2 , the input terminal IO51 of the buffer unit 51 and the input terminal IO53 of the boost unit 52 are both coupled to the chip power pin IO1; the output terminal IO52 of the buffer unit 51 and the output terminal IO54 of the boost unit 52 are both coupled to the power input terminal IO9 of the drive circuit and the chip auxiliary power pin IO2, which are suitable for providing the working voltage for the drive circuit 4. Specifically, when the voltage on the chip auxiliary power pin IO2 has not reached the working voltage of the drive circuit 4, the chip power pin IO1 provides the working voltage to the drive circuit 4 through the buffer unit 51; when the voltage on the chip auxiliary power pin IO2 reaches the working voltage of the drive circuit 4, the chip auxiliary power pin IO2 provides the working voltage to the drive circuit 4.

[0040] In one embodiment, the boost unit includes a charge pump boost circuit. The structure of the charge pump circuit is a well-known technology in the art and will not be described in detail here. It can be understood by those skilled in the art that in other embodiments, the boost unit can also be other circuits with a boost function, which can satisfy the requirement that the low voltage end is used as the input of the boost unit and the high voltage end is used as the output of the boost unit.

[0041] In one embodiment, the buffer unit includes a diode, such as Figure 3 As shown, Figure 3 In one embodiment of the present invention Figure 2 Schematic diagram of the circuit structure of the driving circuit power supply unit 5A. Figure 3 The positive electrode of the diode 51A is coupled to the input end (low voltage end) of the boost unit 52A as the input end IO4A of the drive circuit power supply unit 5A, and the input end IO4A of the drive circuit power supply unit 5A is coupled to the chip power pin IO1; the negative electrode of the diode 51A is coupled to the output end (high voltage end) of the boost unit 52A as the output end IO5A of the drive circuit power supply unit 5A, and the output end IO5A of the drive circuit power supply unit 5A is coupled to the power input end IO9 of the drive circuit and the chip auxiliary power pin IO2.

[0042] Combined with reference Figure 1 andFigure 3 , because the chip power pin IO1 not only supplies power to other modules inside the switching power chip 1, but also serves as the input of the drive circuit power supply unit 5A. When the voltage on the chip power pin IO1 is relatively low, the voltage on the chip power pin IO1 enters the input port IO4A of the drive circuit power supply unit 5A, and then generates a chip auxiliary power supply on the chip auxiliary power pin IO2 through the boosting effect of the boost unit 52A. Since it takes time to generate the chip auxiliary power supply, when the chip auxiliary power supply has not yet met the demand of the drive circuit 4, the chip power pin IO1 first supplies power to the drive circuit 4 through the diode 51A. When the chip auxiliary power supply meets the demand of the drive circuit 4, the buffer unit is closed, that is, the diode 51A is reversely cut off, and the power supply of the drive circuit 4 is completely carried out by the chip auxiliary power supply generated on the chip auxiliary power pin IO2. Due to the boosting effect of the boost unit 51A, the chip auxiliary power supply voltage must be higher than the voltage on the chip power pin IO1, which can meet the voltage demand of the drive circuit 4.

[0043] In another embodiment, the buffer unit includes a first MOS transistor, such as Figure 4 As shown, Figure 4 In another embodiment of the present invention Figure 2 Schematic diagram of the circuit structure of the driving circuit power supply unit 5B. Figure 4 , the gate of the first MOS transistor 51B is coupled to the second output terminal of the control unit 3, and receives the second control signal K2 input by the second output terminal, and the second control signal K2 is used to control the switch of the first MOS transistor 51B; the source of the first MOS transistor 51B is coupled to the input terminal (low voltage terminal) of the boost unit 52B as the input terminal IO4B of the drive circuit power supply unit 5B, and the input terminal IO4B of the drive circuit power supply unit 5B is coupled to the chip power pin IO1; the drain of the first MOS transistor 51B is coupled to the output terminal (high voltage terminal) of the boost unit 52B as the output terminal IO5B of the drive circuit power supply unit 5B, and the output terminal IO5B of the drive circuit power supply unit 5B is coupled to the power input terminal IO9 of the drive circuit and the chip auxiliary power pin IO2.

[0044] Combined with reference Figure 1 and Figure 4, since in addition to powering other modules inside the switch power supply chip 1, the chip power supply pin IO1 also serves as the input of the driving circuit power supply unit 5B. When the voltage on the chip power supply pin IO1 is relatively low, the second control signal K2 controls the first MOS transistor 51B to turn on, and the voltage on the chip power supply pin IO1 enters the input port IO4B of the driving circuit power supply unit 5B. Then, through the boosting effect of the boosting unit 52B, a chip auxiliary power supply is generated on the chip auxiliary power supply pin IO2. Since it takes time to generate the chip auxiliary power supply, before the chip auxiliary power supply reaches the requirements of the driving circuit 4, the chip power supply pin IO1 supplies power to the driving circuit 4 through the first MOS transistor 51B first; when the chip auxiliary power supply reaches the requirements of the driving circuit 4, the buffer unit is turned off, that is, the second control signal K2 controls the first MOS transistor 51B to disconnect, and the power supply of the driving circuit 4 is completely provided by the chip auxiliary power supply generated on the chip auxiliary power supply pin IO2. Due to the boosting effect of the boosting unit 52B, the voltage of the chip auxiliary power supply must be higher than the voltage on the chip power supply pin IO1, which can meet the voltage requirements of the driving circuit 4.

[0045] Figure 5 is a schematic circuit diagram of the driving circuit in an embodiment of the present invention. With reference to Figure 1 and Figure 5 , in one embodiment, the driving circuit 4 includes N NMOS transistors and M PMOS transistors; wherein, the gates of the N NMOS transistors and M PMOS transistors are all coupled together to form a control signal input terminal IO8, and are coupled to the first output terminal IO7 of the control unit 3 to input the first control signal K1; the drains of the N NMOS transistors and M PMOS transistors are all coupled together as the output terminal of the driving circuit 4, and are coupled to the gate IO10 of the power MOS transistor 2; the sources of the N NMOS transistors are all coupled to the chip ground terminal GND1, and the sources of the M PMOS transistors are all coupled together as the power input terminal IO9 of the driving circuit 4, and the driving circuit power supply unit 5 provides a working voltage for it.

[0046] In summary, the voltage conversion circuit provided by the embodiment of the present invention includes a buffer unit and a boost unit. When the voltage on the chip power supply pin is relatively low, the boost unit operates to boost the voltage on the chip power supply pin and generate a chip auxiliary power supply on the chip auxiliary power supply pin. At this time, the voltage on the chip power supply pin supplies power to the drive circuit on the switching power supply chip through the buffer unit. When the voltage output by the boost unit can meet the requirements of the drive circuit, the buffer unit is turned off, and the output of the boost unit supplies power to the drive circuit. Due to the function of the boost unit, the chip auxiliary power supply is higher than the voltage on the chip power supply pin and can meet the requirements of the drive circuit. Further, the voltage conversion circuit further includes an auxiliary power supply capacitor, and the auxiliary power supply capacitor can help store the charge generated at the chip auxiliary power supply pin and improve the power supply capacity of the chip auxiliary power supply pin. And the auxiliary power supply capacitor can be arranged inside or outside the switching power supply chip, with a simple structure and low cost.

[0047] The embodiment of the present invention also provides a non-isolated power supply system. Refer to Figure 6 , Figure 6 to give a circuit structure schematic diagram of the non-isolated power supply system according to an embodiment of the present invention.

[0048] As Figure 6 shown, the non-isolated power supply system includes: a rectification unit 60, an output inductor L1, a feedback diode D10, and a voltage conversion circuit 1B. Among them, the voltage conversion circuit 1B includes a switching power supply chip 11, and the switching power supply chip 11 includes a power MOS transistor 21 and a drive circuit 41, and the drive circuit 41 is adapted to drive the power MOS transistor 21 to operate. The voltage conversion circuit 1B further includes a drive circuit power supply unit, and the drive circuit power supply unit includes a buffer unit 53 and a boost unit 54. In one embodiment, the buffer unit 53 is a buffer diode.

[0049] In one embodiment, the voltage conversion circuit 1B further includes an auxiliary power supply capacitor C10. As Figure 6 shown, the auxiliary power supply capacitor C10 is located outside the switching power supply chip 11, its positive electrode is coupled to the chip auxiliary power supply pin IO21, and its negative electrode is coupled to the chip power supply pin IO11. In other embodiments, the auxiliary power supply capacitor C10 can also be located inside the switching power supply chip 11, and its specific connection method and working principle can refer to the foregoing embodiments and will not be elaborated herein.

[0050] The circuit structure and working principle of the voltage conversion circuit 1B can refer to the foregoing embodiments and will not be elaborated herein.

[0051] Refer to Figure 6, in one embodiment, the input end of the rectification unit 60 is coupled to an external AC power supply AC1, and its output end is coupled to the high-voltage input pin IO31 of the switching power supply core 11. The rectification unit 60 is adapted to rectify the externally input alternating current AC1 into direct current and input the direct current into the high-voltage input pin IO31; the input end of the output inductor L1 is coupled to the chip ground pin GND11 of the switching power supply chip 11, and the output end of the output inductor L1 is coupled to the output end OT1 of the non-isolated power supply system; the positive pole of the feedback diode D10 is coupled to the output end OT1 of the non-isolated power supply system, and the negative pole of the feedback diode D10 is coupled to the chip power supply pin IO11, which is adapted to feedback the output voltage OT1 of the non-isolated power supply system to the chip power supply pin IO11.

[0052] In one embodiment, the switching power supply chip 11 further includes a control unit 31. The control unit 31 includes a first output end IO71, and the first output end IO71 is coupled to the input end IO81 of the drive circuit 41, which is adapted to provide a first control signal for the drive circuit 41. The control unit 31 further includes: a third output end IO73. The third output end IO72 is coupled to the control signal input end of the boost unit 54. The control signal input end is adapted to receive a third control signal K3 and is adapted to control the boost unit 54 to turn on or off: when the voltage at the output end OT1 of the non-isolated power supply system is relatively high, the voltage at the chip power supply pin IO11 can meet the power supply requirement of the drive circuit 41. The third output end IO73 of the control unit 31 outputs the third control signal K3 to turn off the boost unit 54, and the chip power supply pin IO11 supplies power to the drive circuit 41 through the buffer unit 53 of the switching power supply chip 11. When the voltage at the output end OT1 of the non-isolated power supply system is relatively low, the voltage at the chip power supply pin IO11 cannot meet the power supply requirement of the drive circuit 41. The third output end IO73 of the control unit 31 outputs the third control signal K3 to turn on the boost unit 54, and the output end of the boost unit 54 supplies power to the drive circuit 41; at this time, the voltage of the negative pole of the buffer diode 53 is higher than that of the positive pole, and it is in a reverse cut-off state. The voltage on the chip power supply pin IO11 cannot be transmitted to the voltage input end IO91 of the drive circuit 41. Therefore, only the chip power supply auxiliary pin IO21 supplies power to the drive circuit 41.

[0053] In one embodiment, the non-isolated power supply system further includes:

[0054] An output capacitor C20. The positive pole of the output capacitor C20 is coupled to the output end OT1 of the non-isolated power supply system, and its negative pole is coupled to the ground GND12 of the non-isolated power supply system;

[0055] A chip power supply capacitor C30, the positive electrode of the chip power supply capacitor C30 is coupled to the chip power supply pin IO11, and its negative electrode is coupled to the chip ground pin GND11;

[0056] A freewheeling diode D20, the positive electrode of the freewheeling diode D20 is coupled to the ground GND12 of the non-isolated power supply system, and its negative electrode is coupled to the input end of the output inductor.

[0057] In summary, for the voltage conversion circuit provided by the embodiment of the present invention, when the chip power supply voltage is relatively low and cannot drive the power MOS transistor, the driving circuit power supply unit is used to boost the chip power supply voltage, and the boosted voltage is used to drive the power MOS transistor. The boosted driving voltage is generated by the internal power supply of the chip, rather than being generated by external power supply, which is beneficial to reducing the loss of the switching power supply chip and has high conversion efficiency.

[0058] Furthermore, the voltage conversion circuit provided by the embodiment of the present invention further includes an auxiliary power supply capacitor, which can help store the charge generated at the chip auxiliary power supply pin and improve the power supply capacity of the chip auxiliary power supply pin. And the auxiliary power supply capacitor can be arranged inside or outside the switching power supply chip, with a simple structure and low cost.

[0059] Furthermore, the non-isolated power supply system provided by the embodiment of the present invention uses a feedback diode to feedback the output voltage of the non-isolated power supply system to the chip power supply pin of the switching power supply chip, and determines whether to turn on the boosting unit according to the magnitude of the output voltage. The non-isolated power supply system has high voltage conversion efficiency, low system loss and simple structure.

[0060] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention should be subject to the scope defined by the claims.

Claims

1. A voltage conversion circuit, comprising: A switching power supply chip, the switching power supply chip includes a power MOS transistor and a driving circuit, and the driving circuit is adapted to drive the power MOS transistor to work; Characterized in that it further includes: A driving circuit power supply unit, including a boosting unit. When the voltage output by the boosting unit has not reached the operating voltage of the driving circuit, the internal power supply of the switching power supply chip provides the operating voltage for the driving circuit; when the voltage output by the boosting unit reaches the operating voltage of the driving circuit, the voltage output by the boosting unit serves as the operating voltage of the driving circuit; The switching power supply chip further includes: a chip power supply pin, a chip ground pin, and a chip auxiliary power supply pin; The driving circuit power supply unit further includes a buffer unit, the buffer unit includes a first MOS transistor, the input end of the buffer unit is coupled to the chip power supply pin, and the output end of the buffer unit is coupled to the power input end of the driving circuit and the chip auxiliary power supply pin; when the voltage output by the boosting unit has not reached the operating voltage of the driving circuit, the internal power supply of the switching power supply chip provides the operating voltage for the driving circuit through the buffer unit; The gate of the first MOS transistor is coupled to the second output end of the control unit in the switching power supply chip, receives the second control signal input by the second output end, the source of the first MOS transistor is coupled to the chip power supply pin, and the drain of the first MOS transistor is coupled to the power input end of the driving circuit and the chip auxiliary power supply pin; The second control signal is used to control the switch of the first MOS transistor. When the voltage on the chip auxiliary power supply pin has not reached the operating voltage of the driving circuit, the second control signal controls the first MOS transistor to turn on, and the chip power supply pin provides the operating voltage for the driving circuit through the first MOS transistor; when the voltage on the chip auxiliary power supply pin reaches the operating voltage of the driving circuit, the second control signal controls the first MOS transistor to turn off, and the chip auxiliary power supply pin provides the operating voltage for the driving circuit.

2. The voltage conversion circuit according to claim 1, Characterized in that The input end of the boosting unit is coupled to the chip power supply pin, and the output end of the boosting unit is coupled to the chip auxiliary power supply pin and the power input end of the driving circuit.

3. The voltage conversion circuit according to claim 1, Characterized in that It further includes: An auxiliary power supply capacitor, the negative electrode of the auxiliary power supply capacitor is coupled to the chip power supply pin or the chip ground pin, and the positive electrode of the auxiliary power supply capacitor is coupled to the chip auxiliary power supply pin; the auxiliary power supply capacitor is adapted to store the charge generated on the chip auxiliary power supply pin.

4. The voltage conversion circuit according to claim 3, Characterized in that The auxiliary power supply capacitor is integrated inside the switching power supply chip or arranged outside the switching power supply chip.

5. The voltage conversion circuit according to claim 4, Characterized in that The power supply terminal of the control unit is coupled to the chip power supply pin, and the first output terminal of the control unit is coupled to the input terminal of the drive circuit, and is adapted to provide a first control signal to the drive circuit.

6. The voltage conversion circuit according to claim 5, wherein, the first control signal is a switching control signal.

7. The voltage conversion circuit according to claim 2, wherein, the boost unit includes a charge pump boost circuit.

8. The voltage conversion circuit according to claim 5, wherein, the drive circuit includes N NMOS transistors and M PMOS transistors; wherein, the gates of the N NMOS transistors and the M PMOS transistors are all coupled to the first output terminal of the control unit to input the first control signal; the drains of the N NMOS transistors and the M PMOS transistors are all coupled together as the output of the drive circuit and are coupled to the gate of the power MOS transistor; the sources of the N NMOS transistors are all coupled to the chip ground pin, and the sources of the M PMOS transistors are all coupled together as the power input terminal of the drive circuit, and the drive circuit power supply unit provides a working voltage for it.

9. A non-isolated power supply system, comprising: a rectification unit, an output inductor, a feedback diode, characterized in that it further comprises: the voltage conversion circuit according to any one of claims 1-8; wherein, the input terminal of the rectification unit is coupled to an external AC power supply, and its output terminal is coupled to the high-voltage input pin of the switching power supply chip in the voltage conversion circuit, and the rectification unit is adapted to rectify the externally input alternating current into direct current and input the direct current into the high-voltage input pin; the input terminal of the output inductor is coupled to the chip ground pin of the switching power supply chip, and the output terminal of the output inductor is coupled to the output terminal of the non-isolated power supply system; the positive pole of the feedback diode is coupled to the output terminal of the non-isolated power supply system, and the negative pole of the feedback diode is coupled to the chip power supply pin, and is adapted to feedback the output voltage of the non-isolated power supply system to the chip power supply pin.

10. The non-isolated power supply system according to claim 9, wherein, the control unit further includes: a third output terminal, the third output terminal is coupled to the control signal input terminal of the boost unit, and is adapted to control the switch of the boost unit: when the voltage at the output terminal of the non-isolated power supply system is relatively high, the voltage of the chip power supply pin can meet the power supply requirement of the drive circuit, and the third output terminal of the control unit outputs a third control signal to turn off the boost unit, and the chip power supply pin supplies power to the drive circuit through the buffer unit of the switching power supply chip; when the voltage at the output terminal of the non-isolated power supply system is relatively low, the voltage of the chip power supply pin cannot meet the power supply requirement of the drive circuit, and the third output terminal of the control unit outputs a third control signal to turn on the boost unit, and the output terminal of the boost unit supplies power to the drive circuit.

11. The non-isolated power supply system according to claim 9, wherein, it further comprises: An output capacitor, the positive electrode of the output capacitor is coupled to the output terminal of the non-isolated power supply system, and its negative electrode is coupled to the ground of the non-isolated power supply system; A chip power supply capacitor, the positive electrode of the chip power supply capacitor is coupled to the chip power supply pin, and its negative electrode is coupled to the chip ground pin; A freewheeling diode, the positive electrode of the freewheeling diode is coupled to the ground of the non-isolated power supply system, and its negative electrode is coupled to the input end of the output inductor.

Images