Overvoltage protection circuit for bootstrap pin in dc-dc boost chip

Abstract

The application discloses an overvoltage protection circuit for a bootstrap pin in a DC-DC boost chip, characterized in that the circuit comprises a comparison unit and a bootstrap voltage regulating unit. out The comparison unit is connected with an output voltage V out of the DC-DC boost chip, and generates a control signal; and the bootstrap voltage regulating unit is controlled by the control signal to output a regulating voltage and regulate a bootstrap voltage on the bootstrap pin based on the regulating voltage and an output terminal voltage of an inductor in the DC-DC boost circuit. The circuit is simple in structure and low in implementation cost, and can ensure the safety of the bootstrap pin without sacrificing the output voltage range.

Description

Technical Field

[0001] This invention relates to the field of integrated circuits, and more specifically, to an overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip. Background Technology

[0002] Currently, in DC-DC boost converter chips, the BOOST pin and SW pin are often connected via capacitors to maintain stable voltage output. To provide a suitable bootstrap voltage to the BOOST pin, a voltage regulation circuit is typically provided and connected to it. For example, in one embodiment, this voltage regulation circuit generates a regulated voltage of approximately 5V. Therefore, under the combined effect of the SW pin voltage and the regulated voltage, the bootstrap pin can achieve a sufficiently large bootstrap voltage to fully realize its function.

[0003] However, because the voltage at the switching pin is not stable enough, a sufficiently large voltage adjustment is required to maintain a adequate bootstrap voltage. But as the voltage at the inductor output terminal of the DC-DC circuit increases, when the output voltage of the switching pin SW becomes too high, the bootstrap pin voltage reaches a limit that the process can withstand. Without overvoltage protection circuitry in the chip, the bootstrap pin may be damaged due to excessive voltage. Adding overvoltage protection circuitry to the chip would increase the chip area, circuit complexity, and manufacturing cost.

[0004] Furthermore, adding overvoltage protection circuitry to the bootstrap pin will limit the chip's output voltage range. For example, when the bootstrap pin is restricted to below the process limit voltage, the output voltage will not exceed the difference between the limit voltage and the modulation voltage. Therefore, the added overvoltage protection circuitry has an unexpected impact on the output voltage of the DC-DC boost chip itself.

[0005] Therefore, there is an urgent need for a DC-DC boost converter chip that can simultaneously protect the bootstrap pin without affecting the maximum output voltage. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide an overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip. This circuit obtains a comparison between the output voltage and the overvoltage threshold through a comparison unit, and controls the bootstrap voltage control unit to output the voltage of the chip's bootstrap pin.

[0007] The present invention adopts the following technical solution.

[0008] In a first aspect, this invention relates to an overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip, wherein the circuit includes a comparator unit and a bootstrap voltage adjustment unit; the comparator unit is compared with the output voltage V of the DC-DC boost converter chip. out Connection, for use based on output voltage V out The system generates control signals; the bootstrap voltage regulation unit, under the control of the control signals, realizes the output of the regulation voltage, and based on the regulation voltage and the output voltage of the inductor in the DC-DC boost circuit, it realizes the regulation of the bootstrap voltage on the bootstrap pin.

[0009] Preferably, the comparator unit is used to compare the output voltage V. out and overvoltage protection threshold V OVP Compare; when the output voltage V out ≥V OVP When the output control signal is high, the output control signal is high; when the output voltage V... out <V OVP When this occurs, the output control signal is at a low level.

[0010] Preferably, the bootstrap voltage regulation unit includes a voltage conversion circuit and a selection switch S; wherein, the voltage conversion circuit is used to generate a regulation voltage V based on the high and low levels of the control signal. reg A selection switch is used to control and regulate the voltage V based on the control signal of the low-side switching transistor in the DC-DC boost chip. reg Output to the bootstrap pin.

[0011] Preferably, when the output voltage V out ≥V OVP When the control signal is high, the voltage V is adjusted. reg =V reg2 When the output voltage V out <V OVP When the control signal is low, the voltage V is adjusted. reg =V reg1 Among them, V reg1 >V ref2 .

[0012] Preferably, in the DC-DC boost circuit, the high-voltage terminal of the first controller connected to the gate of the high-side switching transistor is related to the bootstrap voltage V. bst Connection, low voltage terminal to switching voltage V sw connect.

[0013] Preferably, in the DC-DC boost circuit, the gate of the low-side switch is connected to the high-voltage terminal of the second controller and the regulating voltage V. ref Connect the low-voltage side to ground.

[0014] Preferably, when the logic unit of the DC-DC boost chip switches to the state of outputting high-side switching transistor control signals and not outputting low-side switching transistor control signals, the selector switch is open, and the bootstrap voltage V of the bootstrap pin is... bst Based on bootstrap capacitor C bst maintain.

[0015] Preferably, when the logic unit of the DC-DC boost chip switches to a state where it does not output the high-side switching transistor control signal but outputs the low-side switching transistor control signal, the selector switch is closed, and the adjustment unit is the bootstrap capacitor C. bst Charging, bootstrap voltage V of the bootstrap pin bst Determined based on the bootstrap voltage regulation unit.

[0016] Preferably, when the output voltage V out ≥V OVP At that time, the bootstrap voltage V bst Maintain at C SW +V reg1 When the output voltage V out <V OVP At that time, the bootstrap voltage V bst Maintain at V SW +V reg2 Among them, V SW This is the output voltage of the inductor in the DC-DC boost circuit, i.e., the switching pin voltage of the DC-DC boost chip.

[0017] A second aspect of the present invention relates to an overvoltage protection method for the bootstrap pin in a DC-DC boost converter chip, wherein the method is implemented using an overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip as described in the first aspect of the present invention.

[0018] The beneficial effect of this invention is that, compared with the prior art, the overvoltage protection circuit of the bootstrap pin in a DC-DC boost chip of this invention can obtain a comparison between the output voltage and the overvoltage threshold through a comparison unit, and control the bootstrap voltage adjustment unit to generate a suitable adjustment voltage to achieve the output voltage of the chip's bootstrap pin. The circuit of this invention has a simple structure and low implementation cost, and can ensure the safety of the bootstrap pin without sacrificing the output voltage range. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overvoltage protection circuit of the bootstrap pin in a DC-DC boost chip according to the present invention.

[0020] Figure 2 This is a schematic diagram of the bootstrap voltage regulation unit in the overvoltage protection circuit of the bootstrap pin in a DC-DC boost chip of the present invention. Detailed Implementation

[0021] The present application will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention, and should not be construed as limiting the scope of protection of the present application.

[0022] Figure 1 This is a schematic diagram of the overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip, as described in the prior art of this invention. Figure 1 As shown, an overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip is disclosed. The circuit includes a comparator unit and a bootstrap voltage adjustment unit. The comparator unit is connected to the output voltage V of the DC-DC boost converter chip. out Connection, for use based on output voltage V out The system generates control signals; the bootstrap voltage regulation unit, under the control of the control signals, realizes the output of the regulation voltage, and based on the regulation voltage and the output voltage of the inductor in the DC-DC boost circuit, it realizes the regulation of the bootstrap voltage on the bootstrap pin.

[0023] refer to Figure 1 As can be seen from the content, the overvoltage protection circuit in this invention is based on a DC-DC boost circuit. The DC-DC boost circuit can be implemented using methods commonly found in existing technologies. For example, the DC-DC boost circuit in this invention can have two switching transistors (high-side and low-side), an inductor L, and a capacitor C. out This circuit uses logic units to control the on / off states of two switching transistors to control the output voltage. The circuit in this invention is based on this circuit.

[0024] In this invention, the comparator unit can receive the output voltage V. out It generates a control signal based on the output voltage to control the magnitude of the regulating voltage at the output of the bootstrap voltage regulating unit.

[0025] In addition, the selection switch in the bootstrap voltage regulation unit can also select whether the regulation voltage is connected to the bootstrap pin based on the signal output by the logic unit in the DC-DC boost circuit that controls the state of the switching transistor.

[0026] In addition, DC-DC circuits can control the voltage of the switching pins based on the state of the high-side and low-side power transistor control signals.

[0027] The adjustable voltage output from the bootstrap voltage regulation unit in this invention can be controlled based on the magnitude of the output voltage Vout generated by the DC-DC circuit. Generally, when the output voltage Vout... out A larger value indicates that the switching voltage V sw The voltage is also relatively high. In this case, the output of the regulating voltage can be reduced to prevent overshoot of the voltage on the bootstrap pin.

[0028] Figure 2 This is a schematic diagram of the bootstrap voltage regulation unit in the overvoltage protection circuit of the bootstrap pin in a DC-DC boost converter chip according to the present invention. Figure 2 As shown, it should be noted that the regulating voltage V in this invention... reg1 and V reg2 This can be implemented using two different LDOs (Low Drop Outputs), and then the voltage regulation can be adjusted according to the selection of the selector. reg1 Or V reg2 The output. The selection unit can be based on the output voltage and the threshold V. OVP Comparison implementation V reg1 and V reg2 The choice.

[0029] Preferably, the comparison unit is used to compare the output voltage V. out and overvoltage protection threshold V OVP Compare; when the output voltage V out ≥V OVP When the output control signal is high, the output control signal is high; when the output voltage V... out <V OVP When this occurs, the output control signal is at a low level.

[0030] It is understood that the comparison unit in this invention can control the control signal. Generally speaking, the output of the control signal, whether high or low, can be determined based on the comparison between the output voltage and the over-voltage protection (OVP) threshold.

[0031] In this invention, when the output voltage V out ≥V OVP At this time, it can be considered that the output voltage is too high, causing the switching pin V to... sw The voltage is too high. To prevent the switching voltage V from being too high... sw Excessive voltage can negatively impact the chip's bootstrap pin voltage. In this case, the control signal can be set to a high level. Conversely, when the output voltage V... out <V OVP When the output voltage is within a reliable range, the control signal can be set to a low level. In this way, the comparator unit can control the bootstrap voltage regulation unit connected to its downstream end.

[0032] Preferably, the bootstrap voltage regulation unit includes a voltage conversion circuit and a selection switch S; wherein, the voltage conversion circuit is used to generate a regulation voltage V based on the high and low levels of the control signal. regA selection switch is used to control and regulate the voltage V based on the control signal of the low-side switching transistor in the DC-DC boost chip. reg Output to the bootstrap pin.

[0033] It is understood that the bootstrap voltage regulation unit in this invention can achieve voltage conversion between different amplitudes through the control signal generated by the comparator unit via the voltage conversion circuit, thereby generating two regulation voltages V with different values. reg1 and V reg2 .

[0034] The selection switch in this invention controls whether the regulated voltage is output to the bootstrap pin based on a separate control mechanism. This separate control refers to controlling the output of the regulated voltage via the control signals of the high-side and low-side switching transistors in the DC-DC boost chip.

[0035] Preferably, when the output voltage V out ≥V OVP When the control signal is high, the voltage V is adjusted. reg =V reg2 When the output voltage V out <V OVP When the control signal is low, the voltage V is adjusted. reg =V reg1 Among them, V reg1 >V reg2 .

[0036] It is understood that in this invention, when the output voltage V out ≥V OVP or V out <V OVP At different times, the high and low levels of the control signal are different, and the value of the regulating voltage is also different. Specifically, it can be set that when the output voltage is greater than the overvoltage threshold, the value of the regulating voltage is lower, and when it is less than the overvoltage threshold, the value of the regulating voltage is higher. Through this control method, the voltage amplitude of the bootstrap voltage regulation unit charging the bootstrap capacitor can be limited when the switching voltage is too high, thereby preventing the bootstrap voltage from becoming too high.

[0037] The DC-DC boost circuit of this invention further includes an inductor L, a first controller Ctrl1, a second controller Ctrl2, a first MOSFET, a second MOSFET, an output capacitor, and a bootstrap capacitor. The first controller and the first MOSFET form a first branch, used to control the on / off state of the first MOSFET based on the high-side switching control signal of the DC-DC boost chip. The second controller and the second MOSFET form a second branch, used to control the on / off state of the second MOSFET based on the low-side switching control signal of the DC-DC boost chip. The inductor L is used to isolate the input voltage V.in And MOSFET, output capacitor C out and bootstrap capacitor C BST Used to control the output voltage V out and bootstrap voltage V BST Stable output.

[0038] It is understood that in this invention, the control of the output voltage Vout and the voltage control of the switch pin SW are achieved by controlling the high-end and low-end switching transistor control signals in the DC-DC boost chip.

[0039] One end of the inductor L is connected to the input voltage V of the DC-DC boost converter chip. in Connections: The other end of the output capacitor is grounded, and the two ends of the bootstrap capacitor are connected to the bootstrap pin and the switch pin, respectively.

[0040] Preferably, in the DC-DC boost circuit, the high-voltage terminal of the first controller connected to the gate of the high-side switching transistor is related to the bootstrap voltage V. bst Connection, low voltage terminal to switching voltage V sw connect.

[0041] It is understood that, in one embodiment of the present invention, the high-side switching transistor is connected in series with the gate of the first controller and the gate of the MOS transistor. Figure 1 The first controller in the DC-DC boost chip can have the same other parameter settings as the second controller whose gate is connected to the low-side switch in the DC-DC boost chip. This means that the two controllers can have the same delay. In this way, the time when the MOS transistor receives the HS_ON and LS_ON control signals is exactly the same, thereby preventing the generation of noise in the system.

[0042] Preferably, in the DC-DC boost circuit, the high-voltage terminal of the second controller connected to the gate of the low-side switching transistor is connected to the regulating voltage V. reg Connect the low-voltage side to ground.

[0043] It is understood that the second controller in this invention is similar to the first controller, both being drive circuits composed of inverters, and their connection to the low-side switching transistor is similar to the connection of components in the high-side switching transistor. The difference lies in the voltages connected to the high and low ends of the two components. The first controller in the first branch is connected to the bootstrap pin because the output voltage Vout of the high-side switching transistor is relatively higher than the output voltage Vsw of the low-side switching transistor. To ensure that the conduction logic of both the high-side and low-side transistors is effective under the control of the first and second controllers, the amplitude of the high-level gate conduction voltage of the high-side transistor needs to be set at Vsw+Vreg to prevent insufficient conduction of the high-side transistor. For the low-side transistor, while saving energy, maintaining the gate conduction voltage at Vreg is sufficient to fully achieve conduction.

[0044] Therefore, when LS_ON has a high-level input signal while HS_ON does not, the circuit can turn on the first MOSFET and turn off the second MOSFET. Conversely, when LS_ON does not have a high-level input signal while HS_ON has a high-level input signal, the states of the two transistors toggle.

[0045] Preferably, when the logic unit of the DC-DC boost chip switches to the state of outputting high-side switch control signals and not outputting low-side switch control signals, the selector switch disconnects the bootstrap voltage V of the bootstrap pin. bst Based on bootstrap capacitor C bst Maintained. When the logic unit of the DC-DC boost chip switches to a state where it does not output the high-side switching control signal but outputs the low-side switching control signal, the selector switch closes, and the adjustment unit is the bootstrap capacitor C. bst Charging, bootstrap voltage V of the bootstrap pin bst Determined based on the bootstrap voltage regulation unit.

[0046] It is understood that the logic unit of the DC-DC boost chip in this invention can control the charging and discharging state of the bootstrap capacitor Cbst based on the on and off states of the selection switch and the first and second MOSFETs. Specifically, when the first MOSFET is off and the second MOSFET is on, the voltage of the switch pin SW is pulled down to ground potential as the low-side switch is turned on, and the inductor L stores energy. At this time, the bootstrap pin BOOST is charged through the bootstrap voltage regulation unit as the selection switch is turned on. After the low-side switch is on for a period of time, the bootstrap capacitor can be charged to the level of the regulation voltage. When the on and off states of the high-side and low-side switches switch instantaneously switch, that is, the first MOSFET is on and the second MOSFET is off, the circuit can gradually increase the output voltage and the switching voltage. Since the bootstrap capacitor was fully charged in the previous time period, the voltage of the upper plate of the bootstrap capacitor increases with the increase of the voltage of the lower plate during this time period, thereby keeping the bootstrap voltage of the bootstrap pin BOOST at Vreg+Vsw.

[0047] Preferably, when the output voltage V out ≥V OVP At that time, the bootstrap voltage V bst Maintain at V SW +V reg1 When the output voltage V out <V OVP At that time, the bootstrap voltage V bst Maintain at V SW +V reg2 Among them, V SWThis is the output voltage of the inductor in the DC-DC boost circuit, i.e., the switching pin voltage of the DC-DC boost chip.

[0048] Furthermore, in this invention, the voltage received by the bootstrap pin varies depending on the state of the control signal output by the comparator unit. It is understood that if the output voltage is too high, the regulating voltage is reduced to Vreg2, while when the output voltage does not exceed the overvoltage protection threshold, the regulating voltage is Vreg1 under normal conditions. In one embodiment of this invention, the regulating voltage Vreg1 can be 5V, and the regulating voltage Vreg2 can be 2.5V.

[0049] In a second aspect, the present invention relates to an overvoltage protection method for the bootstrap pin in a DC-DC boost converter chip. The method is implemented using the overvoltage protection circuit described in the first aspect of the present invention. The method sets two different adjustment voltages, high and low, and determines whether to output a high or low adjustment voltage based on the magnitude of the output voltage Vout, so as to keep the voltage at the output terminal of the bootstrap pin below the threshold.

[0050] The beneficial effects of this invention are that, compared with the prior art, the overvoltage protection circuit for the bootstrap pin in a DC-DC boost chip of this invention can obtain a comparison between the output voltage and the overvoltage threshold through a comparator unit, and control the bootstrap voltage adjustment unit to generate a suitable adjustment voltage to achieve the output voltage of the chip's bootstrap pin. The circuit of this invention has a simple structure, low implementation cost, and can effectively ensure the stability of the bootstrap voltage, while achieving safe protection for the bootstrap pin without adding an overvoltage protection circuit to the bootstrap pin.

[0051] The applicant of this invention has provided a detailed description of the embodiments of the invention in conjunction with the accompanying drawings. However, those skilled in the art should understand that the above embodiments are merely preferred embodiments of the invention. The detailed description is only intended to help readers better understand the spirit of the invention and is not intended to limit the scope of protection of the invention. On the contrary, any improvements or modifications made based on the inventive spirit of the invention should fall within the scope of protection of the invention.

Claims

1. An overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip, characterized in that: The circuit includes a comparator unit and a bootstrap voltage regulation unit; wherein... The comparison unit is compared with the output voltage of the DC-DC boost chip. Connection, used for output voltage and overvoltage protection threshold The comparison is performed to generate control signals; The bootstrap voltage regulation unit, controlled by the control signal, regulates the output voltage. When the output voltage... When the control signal is high, the voltage adjustment... When the output voltage When the control signal is low, the voltage adjustment... ;in, The bootstrap voltage on the bootstrap pin is adjusted based on the regulating voltage and the output voltage of the inductor in the DC-DC boost circuit.

2. The overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip according to claim 1, characterized in that: The comparison unit compares the output voltage. and overvoltage protection threshold The comparison is performed to generate control signals, including: When the output voltage When this time, the output control signal is high. When the output voltage When this occurs, the output control signal is at a low level.

3. The overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip according to claim 2, characterized in that: The bootstrap voltage regulation unit includes a voltage conversion circuit and a selection switch S; wherein... The voltage conversion circuit is used to generate an adjustable voltage based on the high and low levels of the control signal. ; The selection switch is used to control the regulating voltage based on the control signal of the low-side switching transistor in the DC-DC boost chip. Output to the bootstrap pin.

4. The overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip according to claim 3, characterized in that: In the DC-DC boost circuit, the high-voltage terminal of the first controller connected to the gate of the high-side switch is related to the bootstrap voltage. Connection, low voltage terminal and switching voltage connect.

5. The overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip according to claim 4, characterized in that: In the DC-DC boost circuit, the high-voltage terminal of the second controller connected to the gate of the low-side switch is regulated by the voltage. Connect the low-voltage side to ground.

6. The overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip according to claim 5, characterized in that: When the logic unit of the DC-DC boost chip switches to a state where it outputs a high-side switching transistor control signal and does not output a low-side switching transistor control signal, the selection switch is turned off, and the bootstrap voltage of the bootstrap pin is... Based on bootstrap capacitor maintain.

7. The overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip according to claim 6, characterized in that: When the logic unit of the DC-DC boost chip switches to a state where it does not output the high-side switching control signal but outputs the low-side switching control signal, the selection switch closes, and the adjustment unit is the bootstrap capacitor. Charging, the bootstrap voltage of the bootstrap pin Determined based on the bootstrap voltage regulation unit.

8. The overvoltage protection circuit for the bootstrap pin in a DC-DC boost converter chip according to claim 7, characterized in that: When the output voltage At that time, the bootstrap voltage Maintain at ; When the output voltage At that time, the bootstrap voltage Maintain at ; Among them, the This refers to the output voltage of the inductor in the DC-DC boost circuit, which is also the voltage of the switching pin of the DC-DC boost chip.

9. An overvoltage protection method for the bootstrap pin in a DC-DC boost converter chip, characterized in that: The method employs an overvoltage protection circuit for the bootstrap pin of a DC-DC boost chip as described in any one of claims 1-8 to achieve overvoltage protection.

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