CN209659177U - Synchronous rectification switch converter - Google Patents

Abstract

The utility model provides a synchronous rectification switching converter. The synchronous rectification switching converter includes: a main circuit, including a main switching tube and a rectifying switching tube, the main switching tube and the rectifying switching tube are turned on and off complementary to each other, and are used to convert a DC input voltage into a DC output voltage and a control circuit, connected to the main circuit, for providing a first switch control signal and a second switch control signal to the main switch tube and the rectifier switch tube respectively, wherein the control circuit uses the direct current during start-up The input voltage generates a first internal power supply voltage, and a first external power supply voltage is used to generate the first internal power supply voltage after startup, and the first external power supply voltage is smaller than the DC input voltage. The internal power supply mode of the control circuit of the synchronous rectification switching converter adopts a new architecture, and the power supply end is transferred from the high-voltage input end to the low-voltage output end after startup, thereby reducing power consumption and improving system efficiency.

Description

Synchronous Rectification Switching Converter

technical field

The utility model relates to power electronic technology, in particular to a synchronous rectification switching converter.

Background technique

Switching converters are the core components for realizing power conversion in modern electronic equipment. The control module of the switching converter generates a pulse signal with a predetermined duty ratio to control the time ratio of the main switching transistor being turned on and off, so as to maintain the output voltage and/or current stability. In the output stage of the switching converter, a diode is used to rectify the pulse signal, and an output capacitor is used to filter the pulse signal to obtain a smooth DC output voltage. The loss of the switching converter mainly includes the loss of the main switching tube, the loss of the transformer and the loss of the rectifier diode. When the switching converter works in a low-voltage, high-current output state, the conduction voltage drop of the diode is relatively high, resulting in high rectification loss.

In order to improve the efficiency of the switching converter, a synchronous rectification technology can be used, wherein a rectifier switch tube is used instead of a diode, and the rectifier switch tube switches on and off states synchronously with the main switch tube to rectify the pulse signal. The on-resistance of the rectifier switch tube is very low, which can reduce the rectification loss. In the synchronous rectification technology, the control circuit provides the switch control signals of the main switching tube and the rectifying switching tube, so that the main switching tube is used to control the power transmission of the main circuit, and the rectifying switching tube is used to control the rectification process of the output stage. The power supply of the control circuit itself comes from the DC input voltage VIN, which generates a lower power supply voltage VDD through the low-dropout linear regulator.

In high power applications, the main switch tube and the rectifier switch tube are, for example, N-type MOS (metal oxide semiconductor) power tubes. The driving of the main switching tube by the control circuit requires a bootstrap power supply, and the voltage of the bootstrap power supply is generated from the power supply voltage VDD. The power consumption current of the driving part of the control circuit for the main switching tube reaches several milliamperes, or even higher, resulting in excessive power consumption of the control circuit, which reduces the efficiency of the switching converter.

Therefore, it is desired to further improve the power supply circuit for the control circuit in the synchronous rectification switching converter to improve the system efficiency.

Utility model content

In view of this, the purpose of this utility model is to provide a synchronous rectification switching converter, wherein the output voltage of the synchronous rectifier is used to provide a power supply voltage for the internal controller, thereby reducing the power consumption of the control circuit and improving the system efficiency of the switching converter.

According to the first aspect of the present invention, there is provided a synchronous rectification switching converter, including: a main circuit, including a main switching tube and a rectifying switching tube, and the main switching tube and the rectifying switching tube are turned on and off complementary to each other , for converting a DC input voltage into a DC output voltage; and a control circuit, connected to the main circuit, for providing a first switch control signal and a second switch control signal to the main switch tube and the rectifier switch tube respectively, wherein , the control circuit uses the DC input voltage to generate a first internal power supply voltage during startup, and uses a first external power supply voltage to generate the first internal power supply voltage after startup, and the first external power supply voltage is lower than the DC Input voltage.

Preferably, the control circuit includes: a power supply module, which receives the DC input voltage and the first external power supply voltage, generates a first power supply voltage and a second power supply voltage respectively, and converts the first power supply voltage and the One of the second power supply voltages is used as the first internal power supply voltage; and a first control module and a second control module are respectively connected to the power supply modules to obtain the first internal power supply voltage, and respectively generate the The first switch control signal and the second switch control signal.

Preferably, the power supply module includes a first input terminal for receiving the DC input voltage, a second input terminal for receiving the first external power supply voltage, and an output terminal for providing the first internal power supply voltage , the power supply module further includes: a selector for selecting one of the first power supply voltage and the second power supply voltage; a first voltage stabilizing module connected between the first input terminal and the selector between; and a second voltage stabilizing module connected between the second input terminal and the selector.

Preferably, the selector disables the first voltage stabilizing module when the second supply voltage meets the requirements of circuit elements inside the control circuit.

Preferably, the power supply circuit further includes: an undervoltage detection module connected between the second input terminal and the first voltage stabilization module, wherein when the first external power supply voltage is lower than a predetermined reference value, The undervoltage detection module re-enables the first voltage stabilization module.

Preferably, the second input terminal is connected to the output terminal of the main circuit to receive the DC output voltage, and the power supply module uses the DC output voltage as the first external power supply voltage.

Preferably, it further includes a first capacitor connected between the second input terminal and ground.

Preferably, the control circuit includes: a power supply module, receiving the DC input voltage, the first external power supply voltage and the second external power supply voltage, using the DC input voltage to generate a first power supply voltage, and using the first external power supply voltage generating a second supply voltage from an external supply voltage, using one of the first supply voltage and the second supply voltage as the first internal supply voltage, and generating a second internal supply voltage using the second external supply voltage; And a first control module and a second control module, respectively connected to the power supply module, to obtain the first internal power supply voltage and the second internal power supply voltage, and generate the first switch control signal and the The second switch control signal.

Preferably, the power supply module includes a first input end for receiving the DC input voltage, a second input end for receiving the first external power supply voltage, and a first input end for receiving the second external power supply voltage. Three input terminals, a first output terminal providing the first internal power supply voltage, a second output terminal providing the second internal power supply voltage, and an intermediate node connected to the main switching tube and the rectifying switching tube The floating terminal, the power supply module further includes: a high-voltage starting module, connected between the first input terminal and the floating terminal, and used to generate the first power supply voltage; a selector connected to the first The two input terminals and the floating terminal adopt the first external power supply voltage as the second power supply voltage, and select one of the first power supply voltage and the second power supply voltage as the first internal power supply voltage , and provide the first internal power supply voltage at the first output terminal; and a voltage stabilizing module, connected between the third input terminal and the second output terminal, using the second external power supply voltage to generate The second internal supply voltage.

Preferably, the second input terminal and the third input terminal are connected to the output terminal of the main circuit to receive the DC output voltage, and the power supply module uses the DC output voltage as the first external supply voltage and the second external supply voltage.

Preferably, it also includes: a diode, the anode of the diode is connected to the output terminal of the main circuit, and the cathode is connected to the second input terminal; and a first capacitor is connected between the second input terminal and the floating between the ground.

Preferably, it further includes: a second capacitor connected between the third input terminal and ground.

Preferably, the main switching tube and the rectifying switching tube are connected in series between the input terminal of the main circuit and ground, and the main circuit further includes: an inductor connected between the main switching tube and the rectifying switch between the intermediate node of the tube and the output terminal of the main circuit; and an output capacitor connected between the output terminal of the main circuit and ground.

Preferably, the main switching transistor and the rectifying switching transistor are any one selected from metal oxide semiconductor field effect transistors, insulated gate bipolar transistors and bipolar transistors.

According to the second aspect of the utility model, a control method for a synchronous rectification switching converter is provided, the main circuit of the synchronous rectification switching converter includes a main switching tube and a rectifying switching tube, and the control method includes: generating a first An internal power supply voltage; using the first internal power supply voltage to supply power to the control circuit to generate a first switch control signal and a second switch control signal; using the first switch control signal to control the conduction state of the main switch tube; and using the second switch control signal to control the conduction state of the rectifier switch, so that the main switch and the rectifier switch are turned on and off complementary to each other, so as to convert the DC input voltage into a DC output voltage, wherein during start-up, the first internal supply voltage is generated using a DC input voltage, and after start-up, the first internal supply voltage is generated using a first external supply voltage, the first external supply voltage being less than the DC input voltage.

Preferably, the step of generating a first internal power supply voltage includes: using the DC input voltage to generate a first power supply voltage; using the first external power supply voltage to generate a second power supply voltage; and selecting the first power supply voltage and One of the second supply voltages is used as the first internal supply voltage.

Preferably, when the second supply voltage meets the requirements of circuit elements inside the control circuit, the function of generating the first supply voltage is disabled.

Preferably, when the first external power supply voltage is lower than a predetermined reference value, the function of generating the first power supply voltage is reactivated.

Preferably, the DC output voltage is used as the first external power supply voltage.

Preferably, the step of generating a first internal power supply voltage includes: using the DC input voltage to generate a first power supply voltage; using the first external power supply voltage to generate a second power supply voltage; and selecting the first power supply voltage and One of the second supply voltages is used as the first internal supply voltage.

Preferably, the method further includes: generating a second internal power supply voltage by using a second external power supply voltage.

Preferably, the DC output voltage is used as the first external power supply voltage and the second external power supply voltage.

Preferably, the main switching transistor and the rectifying switching transistor are any one selected from metal oxide semiconductor field effect transistors, insulated gate bipolar transistors and bipolar transistors.

According to the synchronous rectification switching converter of the embodiment of the utility model, the internal power supply mode of the control circuit adopts a new architecture, the power supply terminal of the control circuit obtains power consumption current from the high voltage input terminal during startup, and the power supply terminal of the control circuit obtains power consumption current from the high voltage input terminal after startup. The high-voltage input is diverted to the low-voltage output, reducing power consumption and improving system efficiency.

Description of drawings

Through the following description of the embodiments of the present invention with reference to the accompanying drawings, the above and other objects, features and advantages of the present invention will be more clear.

Fig. 1 shows a schematic block diagram of a control circuit of a synchronous rectification switching converter according to the prior art.

Fig. 2 shows a schematic block diagram of the control circuit of the synchronous rectification switching converter according to the first embodiment of the present invention.

Fig. 3 shows a schematic block diagram of a synchronous rectification switching converter according to a second embodiment of the present invention.

4a to 4c respectively show schematic circuit diagrams of a voltage stabilizing module, a selector and an undervoltage detecting module in the synchronous rectifying switching converter shown in FIG. 3 .

Fig. 5 shows a schematic block diagram of a synchronous rectification switching converter according to a third embodiment of the present invention.

FIG. 6 shows a schematic circuit diagram of a voltage stabilizing module in the synchronous rectification switching converter shown in FIG. 5 .

Detailed ways

Various embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. In the various drawings, the same elements are denoted by the same or similar reference numerals. For the sake of clarity, various parts in the drawings have not been drawn to scale.

In the present application, the switch transistor is a transistor that provides a current path in the on state, including any one selected from metal oxide semiconductor field effect transistors, insulated gate bipolar transistors and bipolar transistors. The first end and the second end of the switch tube are respectively high potential end and low potential end on the current path, and the control end is used to receive a driving signal to control the switch tube to be turned on and off.

Below in conjunction with accompanying drawing and embodiment the utility model is further described.

Fig. 1 shows a schematic block diagram of a control circuit of a synchronous rectification switching converter according to the prior art. The main circuit of the synchronous rectification switching converter is not shown in FIG. 1 . The main circuit includes a main switching tube and a rectifying switching tube for converting the DC input voltage VIN into a DC output voltage VOUT. The control circuit 100 includes a power supply module 110 , a first control module 120 and a second control module 130 .

The power supply module 110 includes a voltage stabilizing module 111 , such as a low dropout linear regulator (LDO). The voltage stabilizing module 111 receives a DC input voltage VIN and generates a power supply voltage VDD with a lower voltage value.

The first control module 120 and the second control module 130 are connected to the power supply module 110 to obtain a supply voltage VDD. The first control module 120 and the second control module 130 include, for example, a feedback loop, an error amplifier circuit, a logic circuit, and a driving circuit, respectively, and generate a first switch control signal VG1 and a second switch control signal VG2 according to a feedback signal of the DC output voltage VOUT .

The control circuit 100 adopts a DC input voltage to generate a power supply voltage VDD, and the power consumption current of the first control module 120 used for the main switching tube reaches several milliamperes, or even higher, resulting in excessive power consumption of the control circuit, making the switch conversion The efficiency of the device is reduced.

Fig. 2 shows a schematic block diagram of the control circuit of the synchronous rectification switching converter according to the first embodiment of the present invention. The main circuit of the synchronous rectification switching converter is not shown in FIG. 2 . As described below, the main circuit includes a main switching tube and a rectifying switching tube for converting the DC input voltage VIN into a DC output voltage VOUT. The control circuit 200 includes a power supply module 210 , a first control module 220 and a second control module 230 .

The power supply module 210 includes a first voltage stabilizing module 211 , a second voltage stabilizing module 212 , and a selector 213 . The first voltage stabilizing module 211 is, for example, a low dropout linear regulator (LDO). The first input terminal of the power supply module 210 receives a DC input voltage VIN, the second input terminal receives an external power supply voltage VCC, and the output terminal provides an internal power supply voltage.

In the power supply module 210, the first voltage stabilization module 211 receives the DC input voltage VIN, and generates a first power supply voltage VDD1 with a lower voltage value. The second voltage stabilizing module 212 is, for example, a low dropout linear regulator (LDO). The second voltage stabilizing module 212 receives the external power supply voltage VCC, and generates a second power supply voltage VDD2 with a lower voltage value. The selector 213 is connected with the first voltage stabilizing module 211 and the second voltage stabilizing module 212, respectively receives the first power supply voltage VDD1 and the second power supply voltage VDD2, and selects one of them as the internal power supply voltage VDD.

The first control module 220 and the second control module 230 are connected to the power supply module 210 to obtain an internal power supply voltage VDD. The first control module 220 and the second control module 230 include, for example, a feedback loop, an error amplifier circuit, a logic circuit and a driving circuit, respectively, and generate the first switch control signal VG1 and the second switch control signal VG2 according to the feedback signal of the DC output voltage VOUT . At least some circuit components of the first control module 220 and the second control module 230 need the internal power supply voltage VDD to work normally.

During startup, the system is powered on. The power supply module 210 in the control circuit 200 obtains a DC input voltage VIN, and the first voltage stabilization module 211 generates a first power supply voltage VDD1. After startup, the power supply module 210 in the control circuit 200 can also obtain an external power supply voltage VCC, and the second voltage stabilizing module 212 generates a second power supply voltage VDD2 according to the external power supply voltage VCC. The external power supply voltage VCC is lower than the DC input voltage VIN, but higher than the internal power supply voltage VDD required to maintain the normal operation of the control circuit 200 .

In this application, the external power supply voltage VCC refers to a DC voltage obtained from the outside of the control circuit 200 , such as the DC output voltage VOUT from the output stage of the switching converter. The internal power supply voltage VDD represents the power supply voltage required for the normal operation of the internal circuit components of the control circuit 200 (such as error amplifier circuit, logic circuit and driving circuit).

The selector 213 detects the first power supply voltage VDD1 and the second power supply voltage VDD2. When one of the first power supply voltage VDD1 and the second power supply voltage VDD2 is valid, the selector 213 selects the valid power supply voltage as the internal power supply voltage VDD. When both the first power supply voltage VDD1 and the second power supply voltage VDD2 are valid, the selector 213 selects the second power supply voltage VDD2 as the internal power supply voltage VDD. Since the external power supply voltage VCC used to generate the second power supply voltage VDD2 is smaller than the DC input voltage VIN used to generate the first power supply voltage VDD1, when the second power supply voltage VDD2 is used as the internal power supply voltage VDD, the first Power consumption of the control module 220 and the second control module 230 .

It should be noted that the second voltage stabilizing module 212 is only a preferred circuit module, which mainly depends on whether the external power supply voltage VCC can directly meet the requirements of the first control module 220 and the second control module 230 . If the requirements are met, the second voltage stabilizing module 212 can be omitted, and the external power supply voltage VCC can be directly used as the internal power supply voltage for power supply.

Preferably, when the selector 213 selects the second power supply voltage VDD2 as the internal power supply voltage, the selector 213 disables the first voltage stabilizing module 211 so that the first voltage stabilizing module 211 stops working, further reducing power consumption and improving system efficiency.

Preferably, the power supply module 210 further includes an undervoltage detection module 214 for detecting the external power supply voltage VCC. The undervoltage detection module 214 is connected with the first voltage stabilization module 211 . Further, the undervoltage detection module 211 receives an external power supply voltage VCC, and when the external power supply voltage VCC is lower than a predetermined reference value, the undervoltage detection module 214 re-enables the first voltage stabilizing module 211 to generate the first power supply voltage VDD1. The selector 213 selects the first power supply voltage VDD1 as the internal power supply voltage.

According to the control circuit of this embodiment, the power supply module selects one of the DC input voltage and the external power supply voltage to generate the internal power supply voltage, and when the external power supply voltage can meet the requirements of the circuit components inside the control circuit, the external power supply voltage is used to generate the internal power supply voltage . The external power supply voltage is lower than the DC input voltage, so that the power consumption of the control circuit itself can be saved and the system efficiency can be improved when the external power supply voltage is adopted.

Fig. 3 shows a schematic block diagram of a synchronous rectification switching converter according to a second embodiment of the present invention. The synchronous rectification switching converter 300 includes a main circuit and a control circuit.

As shown in the figure, the synchronous rectification switching converter 300 is a high voltage buck synchronous rectification topology. The main circuit includes a main switching tube M1, a rectifying switching tube M2, an inductor L1 and an output capacitor Co. The main switching tube M1 and the rectifying switching tube M2 are connected in series between the input terminal and the ground. The inductor L1 is connected between the middle node of the main switching tube M1 and the rectifying switching tube M2 and the first end of the output capacitor Co, and the second end of the output capacitor Co is grounded. A DC output voltage VOUT is provided across the output capacitor Co.

The control circuit 200 includes a power supply module 210 , a first control module 220 and a second control module 230 . The first input terminal of the power supply module 210 is connected to the input terminal of the synchronous rectification switching converter 300 to obtain a DC input voltage VIN, and the second input terminal is connected to the output terminal of the synchronous rectification switching converter 300 to obtain a DC output voltage VOUT is used as the external power supply voltage VCC of the power supply module 210 .

During startup, the system is powered on. The control circuit of the synchronous rectification switching converter 300 can only obtain the DC input voltage VIN. The power supply module 210 in the control circuit generates the first power supply voltage VDD1 according to the DC input voltage VIN as the internal power supply voltage VDD of the control circuit. The first control module 220 and the second control module 230 in the control circuit start to work after obtaining the internal power supply voltage VDD, and provide the first switch control signal VG1 and the second switch control signal VG2 respectively, thereby entering a normal working state.

During normal operation after start-up, the main switching tube M1 and the rectifying switching tube M2 of the synchronous rectifying switching converter 300 are turned on and off complementary. When the main switch is turned on, the rectifier switch M2 is turned off, and the DC input voltage VIN charges the inductor L1 and the output capacitor Co through the switch M1, and supplies power to the load. When the main switching tube M1 is turned off, the rectifying switching tube M2 is turned on, and the inductor L1 charges the capacitor Co through the rectifying switching tube M2 and supplies power to the load. The output capacitor Co is used to obtain a smooth DC voltage. The DC output voltage VOUT of the synchronous rectification switching converter 300 is smaller than the DC input voltage VIN.

The control circuit of the synchronous rectification switching converter 300 can simultaneously obtain the DC input voltage VIN and the DC output voltage VOUT. The power supply module 210 in the control circuit generates the second power supply voltage VDD2 according to the DC output voltage VOUT as the internal power supply voltage VDD of the control circuit. The first control module 220 and the second control module 230 in the control circuit start to work after obtaining the internal power supply voltage VDD, and provide the first switch control signal VG1 and the second switch control signal VG2 respectively, so as to maintain a normal working state.

According to the synchronous rectification switching converter of this embodiment, the internal power supply voltage of the control circuit is generated according to the DC input voltage VIN during start-up, and the internal power supply voltage of the control circuit is generated according to the DC output voltage VOUT during normal operation. Since the DC output voltage VOUT is smaller than the DC input voltage, the power consumption of the control circuit itself can be reduced during normal operation, thereby improving system efficiency. Preferably, the first voltage stabilizing module in the power supply module is disabled during normal operation, so as to further reduce the power consumption of the control circuit itself. Since the efficiency of the switching converter itself is very high, the current equivalent to the input terminal of the synchronous rectification switching converter is very small, so the overall efficiency is obviously improved.

4a to 4c respectively show schematic circuit diagrams of a voltage stabilizing module, a selector and an undervoltage detecting module in the synchronous rectifying switching converter shown in FIG. 3 .

The voltage stabilizing modules 212 and 211 have the same circuit structure, and the voltage stabilizing module 211 is taken as an example for illustration. The voltage stabilizing module 211 is, for example, a low dropout linear regulator (LDO), including an operational amplifier AMP, a transistor M11, resistors R11 and R12. The non-inverting input terminal of the operational amplifier AMP receives the reference voltage VBG, the inverting output terminal receives the feedback signal of the first power supply voltage VDD1, and the output terminal is connected to the control terminal of the transistor M11. The transistor M11, the resistors R11 and R12 are connected in series between the input terminal of the DC input voltage VIN and the ground. The intermediate node of the transistor M11 and the resistor R11 provides a first supply voltage VDD1, and the intermediate node of the resistors R11 and R12 provides a feedback signal of the first supply voltage VDD1. The voltage stabilizing module 211 uses a feedback loop to maintain the first power supply voltage VDD1 as a regulated output.

The selector 213 includes diodes D31 and D32, the anodes of which receive the first power supply voltage VDD1 and the second power supply voltage VDD2 respectively, and the cathodes of both are connected to a common node to provide an internal power supply voltage VDD.

The undervoltage detection module 214 includes a comparator CMP, resistors R41 and R42. Resistors R41 and R42 are connected in series between the input terminal of the external power supply voltage VCC and the ground to obtain a sampling signal of the external power supply voltage VCC. The non-inverting input terminal of the comparator CMP receives the sampling signal, the inverting input terminal receives the reference signal VREF, and the output terminal provides the switching signal VSW. When the external power supply voltage VCC is lower than a predetermined reference value, the signal generated by the undervoltage detection module 214 is used to re-enable the voltage regulation module 211 .

Fig. 5 shows a schematic block diagram of a synchronous rectification switching converter according to a third embodiment of the present invention. The synchronous rectification switching converter 400 includes a main circuit and a power supply module 410 . The control circuit includes a power supply module 410 , a first control module 420 and a second control module 430 .

As shown in the figure, the synchronous rectification switching converter 400 is a floating high-voltage buck synchronous rectification topology. The main circuit includes a main switching tube M1, a rectifying switching tube M2, an inductor L1 and an output capacitor Co. The main switching tube M1 and the rectifying switching tube M2 are connected in series between the input terminal and the ground. The inductor L1 is connected between the middle node of the main switching tube M1 and the rectifying switching tube M2 and the first end of the output capacitor Co, and the second end of the output capacitor Co is grounded. A DC output voltage VOUT is provided across the output capacitor Co.

The synchronous rectification switching converter 400 also includes a diode D1, capacitors C1 and C2.

A first end of the capacitor C1 is connected to an input end of the power supply module 410 , and a second end is connected to an intermediate node between the main switching transistor M1 and the rectifying switching transistor M2 . The anode of the diode D1 is connected to the first terminal of the output capacitor Co, and the cathode is connected to the first terminal of the capacitor C1. During normal operation, the DC output voltage VOUT is provided to the capacitor C1 via the diode D1 , and a smooth DC voltage is generated after being filtered by the capacitor C1 , which is used as the first external power supply voltage VCC1 of the power supply module 410 .

The first end of the capacitor C2 is connected to an input end of the power supply module 410, and the second end is grounded, and the DC output voltage VOUT is provided to the capacitor C2, and a smooth DC voltage is generated after being filtered by the capacitor C2, which is used as the second external power supply of the power supply module 410 Voltage VCC2.

The power supply module 410 includes a high voltage starting module 411 , a voltage stabilizing module 412 and a selector 413 . The first input terminal of the power supply module 410 receives a DC input voltage VIN, the second input terminal receives a first external power supply voltage VCC1, the third input terminal receives a second external power supply voltage VCC2, and the output terminal provides internal power supply voltages VDD and VDD3. The power supply module 410 also includes a floating terminal connected to the middle node of the main switching transistor M1 and the rectifying switching transistor M2. The high voltage starting module 411 is connected between the first input terminal and the floating terminal. The voltage stabilizing module 412 is connected between the third input terminal and the second control module 430 .

During startup, the power supply module 410 uses the high voltage startup module 411 to generate the first power supply voltage VDD1 from the DC input voltage VIN. During normal operation after startup, the power supply module 410 uses the DC output voltage VOUT to generate the second power supply voltage VDD2. The selector 413 receives the first power supply voltage VDD1 and the second power supply voltage VDD2 respectively, and selects one of them as the internal power supply voltage VDD. After starting, the voltage stabilizing module 412 starts to work, and the voltage stabilizing module 412 uses the DC output voltage VOUT to generate the third power supply voltage VDD3.

The first control module 420 is connected to the selector 413 to obtain an internal power supply voltage VDD. The first control module 420 includes, for example, a feedback loop, an error amplifier circuit, a logic circuit and a driving circuit, and generates the first switch control signal VG1 according to the feedback signal of the DC output voltage VOUT. At least some circuit elements of the first control module 420 need the internal power supply voltage VDD to work normally.

The second control module 430 is connected with the voltage stabilizing module 412 to obtain a third power supply voltage VDD3 as an internal power supply voltage. The second control module 430 includes, for example, a feedback loop, an error amplifier circuit, a logic circuit and a driving circuit, and generates a second switch control signal VG2 according to the feedback signal of the DC output voltage VOUT. At least some circuit elements of the second control module 430 need the third power supply voltage VDD3 to work normally.

According to the synchronous rectification switching converter of this embodiment, during start-up, the high-voltage start-up module 411 generates a first power supply voltage VDD1 according to the DC input voltage VIN, which is used as the internal power supply voltage VDD of the control module 420 of the main switch M1. After the control module 420 works normally, a stable DC output voltage VOUT is obtained. During normal operation, the DC output voltage VOUT is provided to the capacitor C1 through the diode D1, and a smooth DC voltage is generated after being filtered by the capacitor C1, which is used as the first external power supply voltage VCC1 of the power supply module 410, and the power supply module 410 further generates according to the DC output voltage VOUT The second power supply voltage VDD2 is used for the internal power supply voltage of the control module 420 of the main switch M1. At the same time, the power supply module 410 further generates a third power supply voltage VDD3 according to the DC output voltage VOUT, which is used to rectify the internal power supply voltage of the control module 420 of the switching transistor M2.

Since the DC output voltage VOUT is smaller than the DC input voltage, the power consumption of the control circuit itself can be reduced during normal operation, thereby improving system efficiency.

FIG. 6 shows a schematic circuit diagram of a voltage stabilizing module in the synchronous rectification switching converter shown in FIG. 5 .

The voltage stabilizing module 412 is, for example, a low dropout linear regulator (LDO), including an operational amplifier AMP, a transistor M21, resistors R21 and R22. The non-inverting input terminal of the operational amplifier AMP receives the reference voltage VBG, the inverting output terminal receives the feedback signal of the third power supply voltage VDD3, and the output terminal is connected to the control terminal of the transistor M21. The transistor M21, the resistors R21 and R22 are connected in series between the input terminal of the second external power supply voltage VCC2 and the ground. A third power supply voltage VDD3 is provided at the middle node of the transistor M21 and the resistor R21, and a feedback signal of the third power supply voltage VDD3 is provided at the middle node of the resistors R21 and R22. The voltage stabilizing module 412 uses a feedback loop to maintain the third power supply voltage VDD3 as a regulated output.

It should be noted that in this article, relational terms such as first and second etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is a relationship between these entities or operations. There is no such actual relationship or order between them. Furthermore, the term "comprises", "comprises" or any other variation thereof is intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus comprising a set of elements includes not only those elements, but also items not expressly listed other elements, or also include elements inherent in such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article or apparatus comprising said element.

Embodiments according to the present invention are as described above, and these embodiments do not exhaustively describe all details, nor limit the utility model to only the specific embodiments described. Obviously many modifications and variations are possible in light of the above description. This description selects and specifically describes these embodiments in order to better explain the principle and practical application of the utility model, so that those skilled in the art can make good use of the utility model and the modification and use on the basis of the utility model . The invention is to be limited only by the claims and their full scope and equivalents.

Claims (14)

1. A synchronous rectification switching converter, characterized in that, comprising: The main circuit includes a main switching tube and a rectifying switching tube, the main switching tube and the rectifying switching tube are turned on and off complementary to each other, and are used to convert the DC input voltage into a DC output voltage; and a control circuit, connected to the main circuit, for providing a first switch control signal and a second switch control signal to the main switch tube and the rectifier switch tube respectively, Wherein, the control circuit uses the DC input voltage to generate the first internal power supply voltage during start-up, and uses the first external power supply voltage to generate the first internal power supply voltage after start-up, and the first external power supply voltage is lower than the DC input voltage. 2. The synchronous rectification switching converter according to claim 1, wherein the control circuit comprises: a power supply module, receiving the DC input voltage and the first external power supply voltage, generating a first power supply voltage and a second power supply voltage respectively, and using one of the first power supply voltage and the second power supply voltage as the a first internal supply voltage; and A first control module and a second control module are respectively connected to the power supply module to obtain the first internal power supply voltage, and generate the first switch control signal and the second switch control signal respectively. 3. The synchronous rectification switching converter according to claim 2, wherein the power supply module comprises a first input end for receiving the DC input voltage, a first input end for receiving the first external power supply voltage Two input terminals, and an output terminal providing the first internal power supply voltage, the power supply module also includes: a selector for selecting one of the first supply voltage and the second supply voltage; a first voltage stabilizing module connected between the first input terminal and the selector; and The second voltage stabilizing module is connected between the second input terminal and the selector. 4. The synchronous rectification switching converter according to claim 3, wherein the selector disables the first voltage stabilizing module when the second supply voltage meets the requirements of the circuit elements inside the control circuit . 5. The synchronous rectification switching converter according to claim 3, wherein the power supply module further comprises: an undervoltage detection module, connected between the second input terminal and the first voltage stabilization module, Wherein, when the first external power supply voltage is lower than a predetermined reference value, the undervoltage detection module re-enables the first voltage stabilizing module. 6. The synchronous rectification switching converter according to claim 3, wherein the second input terminal is connected to the output terminal of the main circuit to receive the DC output voltage, and the power supply module connects the The DC output voltage is used as the first external power supply voltage. 7. The synchronous rectification switching converter according to claim 6, further comprising a first capacitor connected between the second input terminal and ground. 8. The synchronous rectification switching converter according to claim 1, wherein the control circuit comprises: a power supply module, receiving the DC input voltage, the first external power supply voltage, and the second external power supply voltage, using the DC input voltage to generate a first power supply voltage, and using the first external power supply voltage to generate a second power supply voltage, using one of the first supply voltage and the second supply voltage as the first internal supply voltage, and generating a second internal supply voltage using the second external supply voltage; and A first control module and a second control module are respectively connected to the power supply module to obtain the first internal power supply voltage and the second internal power supply voltage, and respectively generate the first switch control signal and the The second switch control signal. 9. The synchronous rectification switching converter according to claim 8, wherein the power supply module comprises a first input end for receiving the DC input voltage, a first input end for receiving the first external power supply voltage Two input terminals, a third input terminal for receiving the second external power supply voltage, a first output terminal for providing the first internal power supply voltage, a second output terminal for providing the second internal power supply voltage, and a connection To the floating terminal of the middle node of the main switching tube and the rectifying switching tube, the power supply module further includes: a high-voltage starting module, connected between the first input terminal and the floating terminal, and used to generate the first supply voltage; a selector connected to the second input terminal and the floating terminal, adopting the first external power supply voltage as the second power supply voltage, and selecting one of the first power supply voltage and the second power supply voltage being the first internal supply voltage, and providing the first internal supply voltage at the first output; and A voltage stabilizing module, connected between the third input terminal and the second output terminal, and adopting the second external power supply voltage to generate the second internal power supply voltage. 10. The synchronous rectification switching converter according to claim 9, wherein the second input terminal and the third input terminal are connected to the output terminal of the main circuit to receive the DC output voltage, The power supply module uses the DC output voltage as the first external power supply voltage and the second external power supply voltage. 11. The synchronous rectification switching converter according to claim 10, further comprising: a diode with its anode connected to the output of the main circuit and its cathode connected to the second input; and The first capacitor is connected between the second input terminal and the floating ground. 12. The synchronous rectification switching converter according to claim 10, further comprising: The second capacitor is connected between the third input terminal and ground. 13. The synchronous rectification switching converter according to claim 1, wherein the main switching tube and the rectifying switching tube are connected in series between the input end of the main circuit and the ground, and the main circuit also include: an inductor connected between the intermediate node of the main switching tube and the rectifying switching tube and the output terminal of the main circuit; and an output capacitor connected between the output terminal of the main circuit and ground. 14. The synchronous rectification switching converter according to claim 1, wherein the main switching tube and the rectifying switching tube are respectively selected from metal oxide semiconductor field effect transistors, insulated gate bipolar transistors and bipolar any type of transistor.