CN216819378U - Chip protection circuit applied to DC-DC circuit, DC-DC circuit and power supply equipment - Google Patents

Abstract

The application relates to an electronic circuit, and provides a chip protection circuit applied to a DC-DC circuit and the DC-DC circuit, which comprises a first voltage divider, a second voltage divider, a first voltage divider, a second voltage divider and a control circuit, wherein the first end of the first voltage divider is connected to the output end of the DC-DC circuit, and the second end of the first voltage divider is connected to a drive chip and used for disabling an optional input pin of an internal VCC voltage stabilizer; the first end of the second voltage divider is connected with an input power supply, and the second end of the second voltage divider is connected with the selectable input pin; and a third voltage divider having a first end connected to the selectable input pin and a second end connected to ground; the resistance value of the second voltage divider is larger than that of the first voltage divider, so that no matter the DC-DC circuit is in the establishment stage or the achievement stage of the preset output voltage, the DC-DC circuit drives the chip to work only in one working voltage power supply mode, and the chip damage caused by simultaneous power supply of the inner power supply mode and the outer power supply mode is avoided.

Description

Chip protection circuit applied to DC-DC circuit, DC-DC circuit and power supply equipment

Technical Field

The application belongs to the technical field of electronic circuits, and particularly relates to a chip protection circuit applied to a DC-DC circuit, the DC-DC circuit and power supply equipment.

Background

Currently, a direct current-direct current (DC-DC) circuit is used to convert a DC voltage to output a DC voltage of a target voltage. The DC-DC circuit may adopt different circuit configurations. The DC-DC circuit comprises a driving chip and a transformation circuit. The voltage transformation circuit may be a buck (buck) circuit, a boost (boost) circuit, or a buck-boost circuit.

For example, the DC-DC circuit outputs 12V, and the DC-DC circuit performs voltage reduction on the output voltage of the battery pack to generate 12V direct current, and the 12V direct current is supplied to the outside through a 12V direct current output port, and the 12V direct current output port can be a vehicle charging port. Generally, a DC-DC circuit includes a driving chip and a step-down circuit. The voltage reduction circuit comprises a main switching tube, a follow current switching tube and an inductor, and the driving chip is used for controlling the on-off of the main switching tube and the follow current switching tube so as to control the output voltage.

The driving chip needs power supply to maintain work, wherein the driving chip can be powered by an internal VCC voltage stabilizer, namely, the driving chip generates a working voltage VCC through the internal VCC voltage stabilizer after being input by an input voltage Vin, and can also be powered externally, for example, the driving chip is supplied with the working voltage VCC by an output voltage Vout of a DC-DC circuit after being input by an external device. When external power supply is adopted, the power supply generally adopts the output voltage Vout of the DC-DC circuit to supply power, the output voltage Vout is output to a driving VCCDIS (the optional input of the internal VCC voltage stabilizer is disabled) pin after voltage division, and when the voltage of the VCCDIS pin is greater than the VCCDIS threshold value, the internal VCC voltage stabilizer can be switched off and the external power supply is carried out. However, in the process that the output voltage Vout needs to be increased from 0V to 12V, the voltage at the VCCDIS pin will be below the VCCDIS threshold for a while, and the driving chip is powered by the external circuit and the internal VCC voltage regulator at the same time, which may cause the driving chip and even peripheral devices to be damaged.

SUMMERY OF THE UTILITY MODEL

The application aims to provide a chip protection circuit applied to a DC-DC circuit, the DC-DC circuit and power supply equipment, and aims to solve the problem that a driving chip is damaged due to the fact that the driving chip is located outside and inside and supplies power at the same time when an output voltage of a traditional DC-DC circuit is not expected in an output establishing stage.

A first aspect of the embodiments of the present application provides a chip protection circuit applied to a DC-DC circuit, where the DC-DC circuit includes a driving chip and a transforming circuit; the driving chip is used for driving the voltage transformation circuit to realize the conversion of the input power supply voltage; a VCC voltage stabilizer is arranged in the driving chip and used for converting the voltage of the input power supply input to the driving chip into working voltage in an enabling state so as to maintain the driving chip to work; the bias power supply pin of the driving chip is also connected with the output end of the voltage transformation circuit; the chip protection circuit includes:

a first voltage divider, a first end of which is connected to the output end of the voltage transformation circuit, and a second end of which is connected to an optional input pin of the driving chip for disabling the VCC voltage stabilizer;

the first end of the second voltage divider is connected with the input power supply, and the second end of the second voltage divider is connected with the selectable input pin; and

a third voltage divider, the first end of which is connected to the selectable input pin and the second end of which is connected to the ground;

the resistance value of the second voltage divider is greater than that of the first voltage divider, the second voltage divider is used for providing a forbidden voltage greater than a preset value for the optional input pin before the output voltage of the output end of the voltage transformation circuit is gradually increased from 0V to reach a preset output voltage so as to prohibit the internal VCC voltage stabilizer from providing the working voltage for the driving chip, and after the output voltage of the voltage transformation circuit reaches the preset output voltage, the output voltage provides the forbidden voltage through the first voltage divider.

In an optional embodiment, the chip protection circuit further includes a fourth voltage divider, a first end of the fourth voltage divider is connected to the second end of the first voltage divider and the second end of the second voltage divider, and a second end of the fourth voltage divider is connected to the optional input pin.

In one optional embodiment, the voltage regulator further includes a first amplifying circuit, an input end of the first amplifying circuit is connected to the high-side driving pin of the driving chip, an output end of the first amplifying circuit is connected to the main switching tube of the voltage transformation circuit, and the first amplifying circuit is configured to amplify a driving signal of the main switching tube output by the driving chip and output the amplified driving signal to the main switching tube of the voltage transformation circuit.

In one optional embodiment, the first amplifying circuit includes a first resistor, a first NPN triode, and a first PNP triode, a base of the first NPN triode and a base of the first PNP triode are connected in common and then connected to a second end of the first resistor, a first end of the first resistor serves as an input end of the first amplifying circuit, an emitter of the first NPN triode and an emitter of the first PNP triode are connected in common and serve as an output end of the first amplifying circuit, a collector of the first NPN triode is connected to a first power supply, and a collector of the first PNP triode is grounded.

In one optional embodiment, the second amplifying circuit includes a second resistor, a second NPN transistor, and a second PNP transistor, a base of the second NPN transistor and a base of the second PNP transistor are connected in common and then connected to a second end of the second resistor, a first end of the second resistor serves as an input end of the second amplifying circuit, an emitter of the second NPN transistor and an emitter of the second PNP transistor are connected in common and serve as an output end of the second amplifying circuit, a collector of the second NPN transistor is connected to a second power supply, and a collector of the second PNP transistor is grounded.

In one optional embodiment, the circuit further comprises an anti-reverse circuit; the negative electrode of the anti-reverse circuit is connected to a bias power supply pin of the driving chip, and the positive electrode of the anti-reverse circuit is connected to the output end of the voltage transformation circuit.

A second aspect of the embodiments of the present application provides a DC-DC circuit, which includes a driving chip, a transforming circuit, and the above chip protection circuit applied to the DC-DC circuit.

In one optional embodiment, the voltage transformation circuit includes:

the main switching tube is used for connecting input voltage;

the inductor is used for storing electric energy when the main switching tube is switched on and releasing the electric energy when the main switching tube is switched off;

and the follow current switching tube is connected with one end of the inductor at one end and connected with the ground at the other end and used for providing a follow current path for the inductor when the main switching tube is switched off.

A third aspect of the embodiments of the present application provides a power supply apparatus including a battery pack and the above-described DC-DC circuit, wherein the input power is supplied from the battery pack.

Compared with the prior art, the chip protection circuit, the DC-DC circuit and the power supply device applied to the DC-DC circuit have the beneficial effects that: by arranging two voltage division lines, one of the two voltage division lines is connected with an input power supply to provide a forbidden voltage larger than a preset value for an optional input pin for forbidding the internal VCC voltage stabilizer, so that the DC-DC circuit is ensured to forbid the internal VCC voltage stabilizer to provide working voltage for a driving chip in the process that the output voltage is not expected in the output establishing stage, the driving chip is prevented from being in a state that the external circuit and the internal VCC voltage stabilizer supply power simultaneously, and the driving chip is damaged or even affected to peripheral devices, the other voltage division line is connected with the output voltage of the DC-DC circuit, after the output voltage reaches the preset output voltage, the output voltage provides the forbidden voltage through a first voltage divider, and the internal VCC voltage stabilizer is forbidden to provide the working voltage for the driving chip.

Drawings

Fig. 1 is a schematic circuit diagram of a DC-DC circuit according to an embodiment of the present disclosure;

fig. 2 is a schematic circuit diagram of a DC-DC circuit according to a second embodiment of the present application.

Detailed Description

In order to make the technical problems, technical solutions and advantageous effects to be solved by the present application clearer, the present application is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or be indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or be indirectly connected to the other element.

It will be understood that the terms "length," "width," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," and the like, refer to an orientation or positional relationship illustrated in the drawings for convenience in describing the present application and to simplify description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed and operated in a particular orientation, and thus should not be construed as limiting the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present application, "a plurality" means two or more, and "several" means one or more unless specifically limited otherwise.

Referring to fig. 1, a DC-DC circuit provided in the present embodiment includes a corresponding chip protection circuit, and the DC-DC circuit includes a driving chip 10 and a transforming circuit 20. The driving chip 10 is used for driving the voltage transformation circuit 20 to realize the conversion of the voltage of the input power Vin; a VCC voltage regulator (not shown) is arranged in the driving chip 10, and the VCC voltage regulator is used for converting the voltage of an input power Vin input to the driving chip 10 into a working voltage VCC in an enabled state so as to maintain the driving chip 10 to work; the bias power supply pin 13 of the driver chip 10 is also connected to the output terminal 11 of the transformer circuit 20. The transforming circuit 20 may be a boost (boost) circuit, a buck (buck) circuit, or a boost-buck (boost-buck) circuit. The driving chip 10 may be a constant current driving chip or a constant voltage driving chip.

The chip protection circuit includes a first voltage divider 100, a second voltage divider 200, and a third voltage divider 300. A first end of the first voltage divider 100 is connected to the output end 11 of the voltage transformation circuit 20, and a second end of the first voltage divider 100 is connected to an optional input pin 12 of the driver chip 10 for disabling the VCC voltage regulator; a first end of the second voltage divider 200 is connected to the input power Vin, and a second end of the second voltage divider 200 is connected to the optional input pin 12; a first terminal of the third voltage divider 300 is connected to the optional input pin 12, and a second terminal of the third voltage divider 300 is connected to ground; the resistance of the second voltage divider 200 is greater than that of the first voltage divider 100, the second voltage divider 200 is configured to provide a disable voltage Vdis greater than a preset value to the optional input pin 12 before the output voltage Vout of the output terminal 11 of the transformer circuit 20 gradually increases from 0V to reach a preset output voltage (since the output terminal 11 is connected to the bias power pin 13 of the driver chip 10, at this time, an external circuit directly supplies power to the bias power pin 13 of the driver chip 10 based on the output voltage Vout of the transformer circuit 20), so as to prohibit the VCC voltage regulator from providing the operating voltage VCC to the driver chip 10, and after the output voltage Vout of the transformer circuit 20 reaches the preset output voltage, the output voltage Vout provides the disable voltage Vdis through the first voltage divider 100.

The input power Vin may be an input of the DC-DC circuit (i.e., an input of the transformer circuit 20), and two voltage dividing lines are provided, wherein the voltage dividing line based on the second voltage divider 200 is connected to the input power Vin to provide a disable voltage Vdis greater than a preset value (e.g., 1.25V) to the selectable input pin 12, so as to ensure that the voltage dividing line of the transformer circuit 20 prohibits the VCC voltage regulator from providing the working voltage VCC to the driver chip 10 at the stage when the output voltage Vout does not reach the preset output voltage (e.g., 9V) during the output setup stage, so as to prevent the driver chip 10 from being powered by an external circuit and the VCC voltage regulator at the same time, and thus the driver chip 10 even reaches peripheral devices; the output voltage Vout of the transformer circuit 20 is connected based on the voltage dividing line of the first voltage divider 100, and after the output voltage Vout reaches the preset output voltage, the output voltage Vout provides the disable voltage Vdis through the first voltage divider 100, and the VCC voltage regulator is disabled to provide the operating voltage VCC to the driving chip 10. Therefore, no matter the preset output voltage is established or achieved, the driving chip 10 only works in one working voltage power supply mode, and the chip damage caused by simultaneous power supply of the internal power supply mode and the external power supply mode is avoided.

In one optional embodiment, the chip protection circuit further includes a fourth voltage divider 400, a first end of the fourth voltage divider 400 is connected to the second end of the first voltage divider 100 and the second end of the second voltage divider 200, and a second end of the fourth voltage divider 400 is connected to the optional input pin 12. The fourth voltage divider 400 can be used to match the division ratio among the first voltage divider 100, the second voltage divider 200, and the third voltage divider 300 to adjust the magnitude of the disable voltage Vdis input to the optional input pin 12. Alternatively, the first voltage divider 100, the second voltage divider 200, the third voltage divider 300, and the fourth voltage divider 400 may have adjustable resistance values, and may have a circuit formed by at least one of resistors, capacitors, inductors, semiconductor devices, and the like.

The driver chip 10 is provided with 2 push-pull circuits to drive the main switch Q1 and the freewheeling switch Q2 in the transformer circuit 20. Due to the large current on the main switching tube Q1, the driving chip 10 needs a large driving capability (usually expressed as a large current), so that the internal push-pull circuit is prone to heat and is damaged, and finally the whole chip is damaged.

Referring to fig. 2, in order to solve the above problem, an embodiment of the chip protection circuit of the present application further includes a first amplifying circuit 500, an input end of the first amplifying circuit 500 is connected to the high side driving pin 14 of the driving chip 10, an output end of the first amplifying circuit 500 is connected to the main switching tube Q1 of the transforming circuit 20, and the first amplifying circuit 500 is configured to increase a driving capability of the high side driving pin 14, amplify a driving signal of the main switching tube Q1 output by the driving chip 10, and output the amplified driving signal to the main switching tube Q1 of the transforming circuit 20.

Optionally, the first amplifying circuit 500 is a push-pull circuit, and includes a first resistor R1, a first NPN transistor M1, and a first PNP transistor M2, a base of the first NPN transistor M1 and a base of the first PNP transistor M2 are connected in common to serve as an input terminal of the first amplifying circuit 500, an emitter of the first NPN transistor M1 and an emitter of the first PNP transistor M2 are connected in common to be connected to a second terminal of the first resistor R1, a first terminal of the first resistor R1 serves as an output terminal of the first amplifying circuit 500, a collector of the first NPN transistor M1 is connected to the first power supply, and a collector of the first PNP transistor M2 is grounded. Therefore, the push-pull circuit in the driving chip 10 does not need to directly drive the main switching tube Q1, but only needs to drive the newly added first amplifying circuit 500, the newly added external first amplifying circuit 500 drives the main switching tube Q1, and the conduction power consumption of the external push-pull circuit is small and efficient, so that the loss of the internal push-pull circuit is reduced, and the problem of overheating and then burning out the chip is not easy to occur. The first power source of the first amplifying circuit 500 may be supplied with power from the positive electrode PACK + of the battery PACK.

In one optional embodiment, the chip protection circuit further includes a second amplification circuit 600, an input end of the second amplification circuit 600 is connected to the low-side driving pin 15 of the driving chip 10, an output end of the second amplification circuit 600 is connected to the freewheel switch Q2 of the voltage transformation circuit 20, and the second amplification circuit 600 is configured to improve a driving capability of the low-side driving pin 15, amplify a driving signal of the freewheel switch Q2 output by the driving chip 10, and output the amplified driving signal to the freewheel switch Q2 of the voltage transformation circuit 20.

Optionally, the second amplification circuit 600 is a push-pull circuit, and includes a second resistor R2, a second NPN transistor M3, and a second PNP transistor M4, a base of the second NPN transistor M3 and a base of the second PNP transistor M4 are connected in common and then connected to a second end of the second resistor R2, a first end of the second resistor R2 is used as an input end of the second amplification circuit 600, an emitter of the second NPN transistor M3 and an emitter of the second PNP transistor M4 are connected in common and used as an output end of the second amplification circuit 600, a collector of the second NPN transistor M3 is connected to the second power supply, and a collector of the second PNP transistor M4 is grounded. Optionally, the input terminal of the second amplifying circuit 600 is further connected to the low side driving pin 15 of the driving chip 10 through a resistor. Therefore, the push-pull circuit in the driver chip 10 does not need to directly drive the freewheeling switch Q2, but only needs to drive the newly added second amplifier circuit 600, and the newly added external first amplifier circuit 500 drives the freewheeling switch Q2, so that the conduction power consumption of the external push-pull circuit is small and the efficiency is high, thereby reducing the loss of the internal push-pull circuit and preventing the chip from being overheated and burned out. The second power source may be powered by the positive electrode PACK + of the battery PACK.

The chip protection circuit further includes an anti-reverse circuit 700; the negative electrode of the anti-reverse circuit 700 is connected to the bias power pin 13 of the driving chip 10, and the positive electrode of the anti-reverse circuit 700 is connected to the output terminal 11 of the transforming circuit 20. Optionally, the anti-reverse circuit 700 includes a diode D1. The anti-kickback circuit 700 is used to prevent the voltage of the bias supply pin 13 from being fed back to the optional input pin 12, thereby preventing interference with the disable voltage Vdis.

Referring to fig. 1 and fig. 2, a second aspect of the present invention provides a DC-DC circuit, which includes a driving chip 10, a transforming circuit 20, and the chip protection circuit. The driving chip 10 is used for driving the voltage transformation circuit 20 to realize the conversion of the voltage of the input power Vin; a VCC voltage stabilizer is arranged in the driving chip 10, and the VCC voltage stabilizer is used for converting the voltage of an input power Vin input to the driving chip 10 into a working voltage VCC in an enabling state so as to maintain the driving chip 10 to work; the bias power supply pin 13 of the driving chip 10 is also connected with the output terminal 11 of the voltage transformation circuit 20, and the chip protection circuit is connected to the optional input pin 12 of the driving chip 10.

Further, the first amplification circuit 500 and the second amplification circuit 600 in the chip protection circuit are further respectively connected to a high-side driving pin 14 of the driving chip 10 for driving the main switch Q1 to be turned on and off, a low-side driving pin 15 of the driving chip 10 for driving the freewheeling switch Q2 to be turned on and off, and the anti-reverse circuit 700 is connected to a bias power supply pin 13 of the driving chip 10.

The transforming circuit 20 may be a boost (boost) circuit, a buck (buck) circuit, or a boost-buck (boost-buck) circuit. The driving chip 10 may be a constant current driving chip or a constant voltage driving chip. In one embodiment, the transformer circuit 20 includes a main switch Q1, an inductor L, and a freewheeling switch Q2.

The main switching tube Q1 is used for accessing an input power Vin; one end of an inductor L is connected to the main switching tube Q1, the other end of the inductor L is used as the output end 11 of the transformer circuit 20, and the inductor L is used for storing electric energy when the main switching tube Q1 is switched on and releasing the electric energy when the main switching tube Q1 is switched off; a freewheeling switch Q2 having one end connected to one end of the inductor L and the other end connected to ground, for providing a freewheeling path for the inductor L when the main switch Q1 is turned off;

in the scheme, the current passing through the branch where the main switching tube Q1 is located is much larger than that of the freewheeling switching tube Q2, and therefore, the main switching tube Q1 may be formed by connecting a plurality of MOS tubes in parallel, so that the current flowing through a single MOS tube and the stress generated by the current can be reduced, and the performance requirement on the single MOS tube is reduced. The freewheeling switch Q2 may be a single MOS transistor.

The embodiment of the application also provides power supply equipment, which comprises a battery pack and the above DC-DC circuit, wherein the voltage of the input power Vin can be provided by the battery pack or can be provided by external power supply equipment. For example, when the power supply device is externally connected with the power supply device, the power supply device provides the voltage of the input power Vin as the input power Vin, and when the load such as the power supply device is externally connected with the electronic device, the battery pack in the power supply device serves as the input power Vin to provide the voltage of the input power Vin.

The DC-DC circuit or the power supply equipment provided with the DC-DC circuit is provided with the chip protection circuit, so that the whole system is stable, high in reliability and long in service life.

The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.

Claims (10)

1. A chip protection circuit applied to a DC-DC circuit is characterized in that the DC-DC circuit comprises a driving chip and a transformation circuit; the driving chip is used for driving the voltage transformation circuit to realize the voltage conversion of the input power supply; a VCC voltage stabilizer is arranged in the driving chip and used for converting the voltage of the input power supply input to the driving chip into working voltage in an enabling state so as to maintain the driving chip to work; the bias power supply pin of the driving chip is also connected with the output end of the voltage transformation circuit; the chip protection circuit includes:

a first voltage divider, a first end of which is connected to the output end of the voltage transformation circuit, and a second end of which is connected to an optional input pin of the driving chip for forbidding the VCC voltage stabilizer;

a first end of the second voltage divider is connected with the input power supply, and a second end of the second voltage divider is connected with the selectable input pin; and

a third voltage divider, the first end of which is connected to the selectable input pin and the second end of which is connected to the ground;

the resistance value of the second voltage divider is greater than that of the first voltage divider, the second voltage divider is used for providing a forbidden voltage greater than a preset value for the optional input pin before the output voltage of the output end of the voltage transformation circuit is gradually increased from 0V to reach a preset output voltage so as to prohibit the internal VCC voltage stabilizer from providing the working voltage for the driving chip, and after the output voltage of the voltage transformation circuit reaches the preset output voltage, the output voltage provides the forbidden voltage through the first voltage divider.

2. The chip protection circuit according to claim 1, further comprising a fourth voltage divider, wherein a first end of the fourth voltage divider is connected to the second end of the first voltage divider and the second end of the second voltage divider, and a second end of the fourth voltage divider is connected to the optional input pin.

3. The chip protection circuit according to claim 1, further comprising a first amplification circuit, wherein an input terminal of the first amplification circuit is connected to the high-side driving pin of the driving chip, an output terminal of the first amplification circuit is connected to the main switching tube of the voltage transformation circuit, and the first amplification circuit is configured to amplify a driving signal of the main switching tube output by the driving chip and output the amplified driving signal to the main switching tube of the voltage transformation circuit.

4. The chip protection circuit according to claim 3, wherein the first amplifying circuit comprises a first resistor, a first NPN transistor and a first PNP transistor, a base of the first NPN transistor and a base of the first PNP transistor are connected in common and then connected with a second end of the first resistor, a first end of the first resistor serves as an input end of the first amplifying circuit, an emitter of the first NPN transistor and an emitter of the first PNP transistor are connected in common and serve as an output end of the first amplifying circuit, an NPN collector of the first NPN transistor is connected with a first power supply, and a collector of the first PNP transistor is connected with ground.

5. The chip protection circuit according to claim 1, further comprising a second amplification circuit, wherein an input terminal of the second amplification circuit is connected to the low-side driving pin of the driving chip, an output terminal of the second amplification circuit is connected to the freewheeling switch transistor of the voltage transformation circuit, and the second amplification circuit is configured to amplify a driving signal of the freewheeling switch transistor output by the driving chip and output the amplified driving signal to the freewheeling switch transistor of the voltage transformation circuit.

6. The chip protection circuit according to claim 5, wherein the second amplifying circuit comprises a second resistor, a second NPN transistor, and a second PNP transistor, a base of the second NPN transistor and a base of the second PNP transistor are connected in common and then connected to a second end of the second resistor, a first end of the second resistor serves as an input terminal of the second amplifying circuit, an emitter of the second NPN transistor and an emitter of the second PNP transistor are connected in common and serve as output terminals of the second amplifying circuit, a collector of the second NPN transistor is connected to a second power supply, and a collector of the second PNP transistor is grounded.

7. The chip protection circuit according to claim 1, further comprising an anti-reverse circuit; the negative electrode of the anti-reverse circuit is connected to a bias power supply pin of the driving chip, and the positive electrode of the anti-reverse circuit is connected to the output end of the voltage transformation circuit.

8. A DC-DC circuit comprising a driver chip, a transformer circuit, and a chip protection circuit as claimed in any one of claims 1 to 7 applied to the DC-DC circuit.

9. The DC-DC circuit of claim 8, wherein the transformation circuit comprises:

the main switching tube is used for connecting input voltage;

the inductor is used for storing electric energy when the main switching tube is switched on and releasing the electric energy when the main switching tube is switched off;

and the follow current switching tube is connected with one end of the inductor at one end and connected with the ground at the other end and used for providing a follow current path for the inductor when the main switching tube is switched off.

10. A power supply apparatus comprising a battery pack and a DC-DC circuit as claimed in claim 8 or 9, wherein the input power is supplied from the battery pack.

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