High voltage switching converter

Abstract

The application discloses a high-voltage switching converter, which comprises a driving circuit, a selection circuit and a power stage circuit. The selection circuit receives an input voltage and an output voltage, obtains a reference voltage according to a higher potential between the input voltage and the output voltage when the system starts or shuts down, and provides the reference voltage to an isolation region of a high-voltage side transistor in the power stage circuit, so that the potential of the isolation region of the high-voltage side transistor is equal to the high potential between the input voltage and the output voltage, and the occurrence of leakage caused by the conduction of a parasitic PNP transistor in the high-voltage side transistor is avoided, and the ability and safety of the chip in the start-up with load or the shutdown with load are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of switching power supply, more particularly, to a high-voltage switching converter. BACKGROUND

[0002] Switching converters are used to convert input voltage to predetermined output voltage for supplying loads. Existing switching converters include a main switch, a synchronous switch, an inductor and a driving circuit. The driving circuit is used to control the on and off states of the main switch and the synchronous switch, so that the inductor alternately stores and supplies electric energy, thereby generating output voltage and / or output current.

[0003] Figure 1 A structure diagram of a high-voltage switching converter of the prior art is shown. The switching converter adopts Boost topology. The switching converter 100 includes an inductor L1, a high-voltage side transistor M1, a low-voltage side transistor M2, an output capacitor Cout and a driving circuit 110. The inductor L1 and the high-voltage side transistor M1 are connected in series between an input voltage Vin and an output voltage Vout, a first end of the low-voltage side transistor M2 is connected to a node between the inductor L1 and the high-voltage side transistor M1, a second end is grounded, and the output capacitor Cout is connected between the output voltage Vout and the ground. The driving circuit 110 is used to control the on and off of the high-voltage side transistor M1 and the low-voltage side transistor M2.

[0004] Figure 2 A device structure diagram of the high-voltage switching converter of the prior art is shown. As shown in Figure 2 , the high-voltage side transistor M1 and the low-voltage side transistor M2 in the switching converter 200 are both formed in a P-type substrate PSUB, both of which include a P-type body region Pbody, a source region N+ and a drain region N+ located in the P-type body region, a gate dielectric layer and a gate conductor (not labeled) located on the gate dielectric layer, and an isolation region NBL for realizing isolation. The drain electrode D of the high-voltage side transistor M1 is connected to the output voltage Vout, the source electrode S is connected to the node of the substrate electrode, and the drain electrode of the low-voltage side transistor M2 is connected to the node of the substrate electrode. The connection node of the two is connected to one end of the inductor L1, the other end of the inductor L1 is connected to the input voltage Vin, and the node of the source electrode S and the substrate electrode of the low-voltage side transistor M2 is connected to the reference ground voltage GND. Figure 2 In the device structure shown in

[0005] , the high-voltage side transistor M1 has two parasitic devices, one is a parasitic diode D1 formed by the P-type body region Pbody and the drain region N+, and the other is a PNP transistor Q1 formed by the P-type body region Pbody, the isolation region NBL and the P-type substrate PSUB. Figure 2 Figure 2 ​In the normal working process of the device structure shown, the potential of the output voltage Vout is high, the isolation region NBL is connected with the output voltage Vout, and the parasitic diode D1 and the PNP transistor Q1 in the high-side transistor M1 will not be turned on. However, when the system is starting or shutting down, the potential of the output voltage Vout is low, which causes the potential of the isolation region NBL to be lower than the potential of the P-type body region Pbody, and thus there is a stage in which the parasitic diode D1 is turned on, at which time VPbody-Vout=Vdiode. However, since the isolation region NBL is short-circuited with the output voltage Vout, the potential of the base B of the PNP transistor Q1 is also lower than the potential of the emitter E, which in turn causes the PNP transistor Q1 to be turned on, resulting in leakage of the system, and even the risk of burning out the chip during the process of starting or shutting down under heavy load. SUMMARY

[0006] In view of the above problems, the purpose of the present application is to provide a high-voltage switching converter, which solves the problem of leakage caused by the turn-on of the parasitic PNP transistor in the high-voltage transistor, and improves the ability and safety of the chip during the process of starting or shutting down under load.

[0007] According to an embodiment of the present application, a high-voltage switching converter is provided, which comprises: a power stage circuit comprising an inductor and a high-voltage transistor and a low-voltage transistor connected therewith, the inductor and the high-voltage transistor being connected in series between an input voltage and an output voltage, and the low-voltage transistor being connected between the inductor and a middle node of the high-voltage transistor and the ground; a driving circuit for controlling the turn-on and turn-off of the high-voltage transistor and the low-voltage transistor; and a selection circuit for obtaining a reference voltage according to the higher potential of the input voltage and the output voltage when the circuit is starting or shutting down, and providing the reference voltage to an isolation region of the high-voltage transistor.

[0008] Optionally, the isolation region is used to realize the isolation between the transistor and the substrate.

[0009] Optionally, the selection circuit comprises: a first diode, the anode of which is connected with the input voltage, and the cathode of which is connected with the output end of the reference voltage; and a second diode, the anode of which is connected with the output voltage, and the cathode of which is connected with the output end of the reference voltage.

[0010] Optionally, when the input voltage is greater than the output voltage, the first diode is turned on, the second diode is turned off, and the reference voltage is equal to the voltage difference between the input voltage and a preset voltage; when the input voltage is less than the output voltage, the first diode is turned off, the second diode is turned on, and the reference voltage is equal to the voltage difference between the output voltage and the preset voltage.

[0011] Optionally, the preset voltage is equal to the voltage drop of the first diode and the second diode.

[0012] The high-voltage switching converter of the embodiment of the application comprises a driving circuit, a selection circuit and a power stage circuit, the selection circuit receives an input voltage and an output voltage, and obtains a reference voltage according to the higher potential between the input voltage and the output voltage when the system starts or shuts down, and provides the reference voltage to the isolation region of the high-voltage side transistor in the power stage circuit, so that the potential of the isolation region of the high-voltage side transistor is equal to the higher potential between the input voltage and the output voltage, avoiding the occurrence of leakage caused by the conduction of the parasitic PNP transistor in the high-voltage side transistor, and improving the ability and safety of the chip in the start-up or shutdown under load. BRIEF DESCRIPTION OF DRAWINGS

[0013] The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments of the present application taken in conjunction with the accompanying drawings, in which:

[0014] Figure 1 Fig. 1 shows a structure schematic diagram of a switching converter according to the prior art;

[0015] Figure 2 Fig. 2 shows a device structure diagram of a high-voltage switching converter according to the prior art;

[0016] Figure 3 Fig. 3 shows a structure schematic diagram of a high-voltage switching converter according to the embodiment of the present application;

[0017] Figure 4 Fig. 4 shows a structure schematic diagram of a selection circuit in a high-voltage switching converter according to the embodiment of the present application. DETAILED DESCRIPTION

[0018] Various embodiments of the present application will be described in detail with reference to the drawings, below. In the various drawings, the same elements are denoted by the same or similar reference numerals. For the sake of clarity, each portion in the drawings is not drawn to scale.

[0019] It should be understood that, in the following description, "circuit" refers to a conductive loop formed by at least one element or sub-circuit through electrical or electromagnetic connection. When an element or circuit is said to be "connected to" another element or said to be "connected between" two nodes, it can be directly coupled or connected to another element or there can be intermediate elements, and the connection between elements can be physical, logical or a combination thereof. In contrast, when an element is said to be "directly coupled to" or "directly connected to" another element, it means that there is no intermediate element between the two.

[0020] In the present application, the switch tube is a transistor working in switch mode to provide a current path, including one selected from bipolar transistor or field effect transistor. The first end and the second end of the switch tube are high potential end and low potential end on the current path respectively, and the control end is used to receive a driving signal to control the on and off of the switch tube. The present application is further illustrated below in combination with the drawings and embodiments.

[0021] Figure 3 A circuit schematic diagram of a high voltage switch converter according to an embodiment of the present application is shown. The switch converter 300 includes a driving circuit 310, a selection circuit 320 and a power stage circuit. The power stage circuit includes an inductor L1, a high voltage side transistor M1, a low voltage side transistor M2 and an output capacitor Cout. The inductor L1 and the high voltage side transistor M1 are connected in series between an input voltage Vin and an output voltage Vout, the first end of the low voltage side transistor M2 is connected to a node between the inductor L1 and the high voltage side transistor M1, the second end is grounded, and the output capacitor Cout is connected between the output voltage Vout and the ground.

[0022] The driving circuit 310 is used to control the on and off of the high voltage side transistor M1 and the low voltage side transistor M2. For example, the driving circuit 310 is connected to the control end G of the high voltage side transistor M1 and the low voltage difference transistor M2 to provide a driving signal, such as a duty cycle signal, to the high voltage side transistor M1 and the low voltage side transistor M2. The high voltage side transistor M1 and the low voltage side transistor M2, for example, are N-type field effect transistors, which are alternately turned on and off in each switching cycle, so that the inductor L1 alternately stores and supplies electric energy. When the switch converter 300 starts to work, the high voltage side transistor M1 is turned off, the low voltage side transistor M2 is turned on, and the inductor L1 starts to store electric energy. Then the high voltage side transistor M1 is turned on, the low voltage side transistor M2 is turned off, and the inductor L1 starts to supply electric energy to the output capacitor Cout, so that the output voltage Vout gradually rises.

[0023] The selection circuit 220 receives the input voltage Vin and the output voltage Vout, and is used to obtain a reference voltage Vmax according to the higher potential between the input voltage Vin and the output voltage Vout when the system starts or turns off, and provide the reference voltage Vmax to the isolation region NBL of the high voltage side transistor M1, so that the potential of the isolation region NBL of the high voltage side transistor M1 is equal to the high potential of the input voltage Vin and the output voltage Vout, avoiding the occurrence of leakage caused by the conduction of the parasitic PNP transistor in the high voltage side transistor M1.

[0024] Further, the isolation region NBL is used to realize the isolation between the transistor and the P-type substrate PSUB.

[0025] Further, the high-voltage side transistor M1 further comprises a P-type substrate PSUB, and the P-type substrate PSUB of the high-voltage side transistor M1 is grounded.

[0026] Further, when the output voltage Vout is greater than the input voltage Vin, for example, the input voltage Vin = 5V, and the output voltage Vout = 10V. The parasitic diode D1 in the high-voltage side transistor M1 is not conductive, and for the PNP transistor Q1, VE-VB = VPbody-VNBL = VPbody-Vout. Since the on-voltage drop of the high-voltage side transistor M1 is very small, the potential of the P-type body region Pbody is approximately equal to the output voltage Vout, which is equivalent to the short circuit of the base B and the emitter E of the PNP transistor Q1, i.e. the parasitic PNP transistor is not conductive.

[0027] When the output voltage Vout is less than the input voltage Vin, for example, the input voltage Vin = 5V, and the output voltage Vout = 1V. The parasitic diode D1 in the high-voltage side transistor M1 is conductive, and at this time, VPbody-Vout = Vdiode. For the PNP transistor Q1, VE-VB = VPbody-VNBL = VPbody-Vin = Vout+Vdiode-Vin < 0, so the parasitic PNP transistor is not conductive.

[0028] Figure 4 A structure diagram of a selection circuit in a high-voltage switching converter according to an embodiment of the present application is shown. As shown in Figure 4 The selection circuit 320 comprises diodes D2 and D3, the anode of the diode D2 is connected with the input voltage Vin, and the cathode is connected with the output end of the reference voltage Vmax. The anode of the diode D3 is connected with the output voltage Vout, and the cathode is connected with the output end of the reference voltage Vmax. When the input voltage Vin is greater than the output voltage Vout, the diode D2 is conductive, the diode D3 is cut off, and the reference voltage Vmax = Vin-Vdiode; when the input voltage Vin is less than the output voltage Vout, the diode D2 is cut off, the diode D3 is conductive, and the reference voltage Vmax = Vout-Vdiode, wherein Vdiode represents the voltage drop of the diode D2 and the diode D3.

[0029] In summary, the high-voltage switching converter of the embodiment of the present application comprises a driving circuit, a selection circuit and a power stage circuit, the selection circuit receives input voltage and output voltage, and is used to obtain a reference voltage according to the higher potential between the input voltage and the output voltage when the system starts or shuts down, and provide the reference voltage to the isolation region of the high-voltage side transistor in the power stage circuit, so that the potential of the isolation region of the high-voltage side transistor is equal to the higher potential between the input voltage and the output voltage, avoiding the occurrence of leakage caused by the conduction of the parasitic PNP transistor in the high-voltage side transistor, and improving the ability and safety of the chip in the load start or load shutdown.

[0030] The implementation principle of the switching converter of the embodiment of the present application is described above. Similarly, the present application can also be applied to the control method of the switching converter. For the high-voltage switching converter, the higher potential between the input voltage and the output voltage is provided to the isolation region of the high-voltage side transistor, avoiding the occurrence of leakage caused by the conduction of the parasitic PNP transistor in the high-voltage side transistor, and being conducive to improving the ability and safety of the chip in the load start or load shutdown.

[0031] According to the above description of the embodiments of the present application, these embodiments do not describe all the details, and the present application is not limited to the specific embodiments. Obviously, according to the above description, many modifications and changes can be made. The present application selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well utilize the present application and make modifications and uses on the basis of the present application. The protection scope of the present application should be limited by the scope defined by the claims of the present application.

Claims

1. A high-voltage switchgear, comprising: A power stage circuit includes an inductor and a high-side transistor and a low-side transistor connected thereto. The inductor and the high-side transistor are connected in series between the input voltage and the output voltage, and the low-side transistor is connected between the intermediate node of the inductor and the high-side transistor and ground. A driving circuit is used to control the on and off states of the high-voltage side transistor and the low-voltage side transistor; as well as A selection circuit is configured to, when the circuit is turned on or off, obtain a reference voltage based on the higher of the input voltage and the output voltage, and provide the reference voltage to the isolation region of the high-voltage-side transistor, wherein the isolation region is used to achieve isolation between the transistor and the substrate. The selection circuit includes: A first diode, with its anode connected to the input voltage and its cathode connected to the output terminal of the reference voltage; and The second diode has its anode connected to the output voltage and its cathode connected to the output terminal of the reference voltage. When the input voltage is greater than the output voltage, the first diode is turned on and the second diode is turned off, and the reference voltage is equal to the voltage difference between the input voltage and a preset voltage; When the input voltage is less than the output voltage, the first diode is turned off and the second diode is turned on, and the reference voltage is equal to the voltage difference between the output voltage and the preset voltage.

2. The high-voltage switchgear according to claim 1, wherein, The preset voltage is equal to the voltage drop across the first diode and the second diode.

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