Over-current protection circuit for DC-DC converter and DC-DC converter system

Abstract

The utility model discloses an overcurrent protection circuit for a DC-DC converter and a DC-DC converter system. An overcurrent protection circuit for a DC-DC converter comprises a current sampling circuit, a comparator circuit, a bus transceiver circuit, a driving circuit, a first pull-down circuit and a second pull-down circuit. The current sampling circuit can be used for carrying out current sampling on the DC-DC converter and outputting a first voltage signal. The comparator circuit may compare the first voltage signal with a reference voltage signal to output a second voltage signal. The bus transceiver circuit may receive the second voltage signal and control the drive signal thereof output in response to the second voltage signal. The driving circuit can receive and convert the driving signal and provide the converted driving signal to a switching tube in the DC-DC converter. The first pull-down circuit may be connected to an output of the bus transceiver circuit, and the second pull-down circuit may be connected to an input of the driver circuit.

Description

Technical Field

[0001] The present application relates to the field of circuit protection, and in particular to an overcurrent protection circuit for a DC-DC converter and a DC-DC converter system. Background Art

[0002] In power circuits, protection circuits are an important part of the circuit system, and determine the reliability and safety of a product. When a component in a DC-DC converter or an abnormal load occurs, if the drive signal cannot be quickly and reliably blocked to stop working in time, the instantaneous high current will cause permanent damage to components such as semiconductors, and the semiconductor devices in the DC-DC converter do not have the ability to withstand long-term overload and / or overcurrent.

[0003] Therefore, a protection circuit is needed that can quickly and reliably shut down a driving signal. Utility Model Content

[0004] In order to solve the above technical problems, the present application provides an overcurrent protection circuit for a DC-DC converter and a DC-DC converter system.

[0005] According to one aspect of the present application, an embodiment provides an overcurrent protection circuit for a DC-DC converter, comprising: a current sampling circuit, a comparator circuit, a bus transceiver circuit, a drive circuit, a first pull-down circuit, and a second pull-down circuit;

[0006] The current sampling circuit comprises a coupling end and an output end, the current sampling circuit is coupled to the DC-DC converter through its coupling end to perform current sampling on the DC-DC converter, and outputs a first voltage signal through its output end;

[0007] The comparator circuit comprises a first input terminal, a second input terminal and an output terminal. The comparator circuit is connected to the output terminal of the current sampling circuit through its first input terminal to receive the first voltage signal, receives a reference voltage signal through its second input terminal, compares the first voltage signal with the reference voltage signal and outputs a second voltage signal through its output terminal.

[0008] The bus transceiver circuit comprises a control terminal and an output terminal, wherein the bus transceiver circuit is connected to the output terminal of the comparator circuit through the control terminal to receive the second voltage signal, and in response to the second voltage signal, outputs a driving signal through the output terminal or stops the output terminal from outputting the driving signal and is in a high impedance state;

[0009] The driving circuit comprises an input end and an output end, wherein the driving circuit is connected to the output end of the bus transceiver circuit through its input end to receive and transform the driving signal, and provides the transformed driving signal to the switch tube in the DC-DC converter through its output end;

[0010] The first pull-down circuit includes a first end and a second end, the first pull-down circuit is connected to the output end of the bus transceiver circuit through its first end and is grounded through its second end;

[0011] The second pull-down circuit includes a first terminal and a second terminal, and the second pull-down circuit is connected to the input terminal of the driving circuit through the first terminal and is grounded through the second terminal.

[0012] In some embodiments, when the first voltage signal is less than the reference voltage signal, the second voltage signal is a low level signal, and when the first voltage signal is greater than the reference voltage signal, the second voltage signal is a high level signal.

[0013] In some embodiments, the control end of the bus transceiver circuit includes an enable end. When the second voltage signal is a low level signal, the enable end enables the output end of the bus transceiver circuit to output the drive signal. When the second voltage signal is a high level signal, the enable end enables the output end of the bus transceiver circuit to stop outputting the drive signal and be in a high impedance state.

[0014] In some embodiments, the DC-DC converter includes a transformer, the coupling end of the current sampling circuit includes a mutual inductor, the mutual inductor is coupled to the transformer, and the mutual inductor includes a first end and a second end;

[0015] The current sampling circuit also includes a bridge rectifier circuit and a first resistor;

[0016] The first resistor includes a first end and a second end;

[0017] The bridge rectifier circuit comprises a first diode, a second diode, a third diode and a fourth diode connected in a bridge manner, a node between an anode of the first diode and a cathode of the second diode serving as a first input terminal, a node between an anode of the third diode and a cathode of the fourth diode serving as a second input terminal, a node between a cathode of the first diode and a cathode of the third diode serving as a positive output terminal, and a node between an anode of the second diode and an anode of the fourth diode serving as a negative output terminal;

[0018] The bridge rectifier circuit is connected to the first end of the mutual inductor through its first input end, connected to the second end of the mutual inductor through its second input end, connected to the first end of the first resistor through its positive output end, and connected to the second end of the first resistor and grounded through its negative output end;

[0019] The positive output terminal of the bridge rectifier circuit is connected to the first input terminal of the comparator circuit as the output terminal of the current sampling circuit.

[0020] In some embodiments, the driving circuit includes a driving chip and a peripheral circuit, the driving chip includes an input terminal and an output terminal, and is connected to the input terminal of the driving circuit through its input terminal, and is connected to the output terminal of the driving circuit through its output terminal, the peripheral circuit includes a capacitor, the capacitor includes a first terminal and a second terminal, the capacitor is connected to the input terminal of the driving chip through its first terminal and is grounded through its second terminal.

[0021] In some embodiments, the first pull-down circuit and the second pull-down circuit each include a pull-down resistor in the kilo-ohm range.

[0022] In some embodiments, the bus transceiver circuit includes a dual power bus transceiver 245 chip circuit.

[0023] In some embodiments, the switch tube in the DC-DC converter includes a MOSFET tube, and the converted drive signal is provided to a control electrode of the MOSFET tube.

[0024] In some embodiments, the drive signal comprises a pulse width modulated signal.

[0025] According to another aspect of the present application, an embodiment provides a DC-DC converter system, including a DC-DC converter and an overcurrent protection circuit according to any of the above embodiments.

[0026] According to the overcurrent protection circuit and DC-DC converter system of the above-mentioned embodiment, since the pull-down circuits are respectively connected to the output end of the power bus transceiver circuit and the input end of the driving circuit for the power device, the driving signal can be reliably and quickly shut down, thereby providing a fast and reliable protection function when an overcurrent occurs in the DC-DC converter. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 is a schematic diagram of an overcurrent protection circuit 120 according to an embodiment;

[0028] Figure 2 FIG. 2 is a top view of a dual power bus transceiver 245 chip 200 according to an embodiment;

[0029] Figure 3 3 is a circuit diagram of a current sampling circuit 310, a comparator circuit 320 and a dual power bus transceiver 245 chip circuit 330 in an overcurrent protection circuit of an embodiment;

[0030] Figure 4 is a circuit diagram of a driving circuit 400 in an overcurrent protection circuit according to an embodiment;

[0031] Figure 5 FIG. 5 is a block diagram of a DC-DC converter system 500 according to an embodiment. DETAILED DESCRIPTION

[0032] The present application is further described in detail below by specific embodiments in conjunction with the accompanying drawings. Wherein similar elements in different embodiments adopt associated similar element numbers. In the following embodiments, many detailed descriptions are intended to enable the present application to be better understood. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, and methods. In some cases, some operations related to the present application are not shown or described in the specification, in order to avoid the core part of the present application being overwhelmed by too much description, and for those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the description in the specification and the general technical knowledge in the art.

[0033] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementations, and the operation steps involved in each embodiment can also be replaced or adjusted in a sequence in a manner that is obvious to those skilled in the art. Therefore, the specification and drawings are only for the purpose of clearly describing a certain embodiment and do not mean that the composition and / or sequence are necessary.

[0034] The serial numbers of the components in this document, such as "first", "second", etc., are only used to distinguish the objects described and do not have any order or technical meaning. The "connection" and "coupling" mentioned in this application, unless otherwise specified, include direct and indirect connections (couplings).

[0035] At present, bus transceiver circuits are widely used in protection circuits of DC-DC converters, especially using the output enable pin of the bus transceiver circuit to block the driving signal (for example, a pulse width modulation (PWM) signal) to achieve a protection function, wherein the bus transceiver circuit may include a dual-power bus transceiver 245 chip. For example, a current sampling circuit may be used to convert a current signal into a voltage signal, and a comparator circuit may be used to compare the voltage signal with a reference voltage, and then a level signal may be output, and the level signal may be sent to the output enable pin of the dual-power bus transceiver 245 chip. Thereby, the driving signal of the output end of the dual power bus transceiver 245 chip is blocked, thereby realizing the overcurrent protection function.

[0036] In the application of the dual power bus transceiver 245 chip, its output port is in a high impedance state, and a pull-down resistor can be added at its output end, but this will have the following problems:

[0037] 1) When the DC-DC converter fails and loses power or the dual power bus transceiver 245 chip fails, the driving signal at the output end of the dual power bus transceiver 245 chip will be uncertain, and there is a risk of mis-conduction of the MOSFET;

[0038] 2) In a DC-DC converter, the dual power bus transceiver 245 chip is generally close to the control end, and its output drive signal is far away from the power end. It is unreliable to simply add a pull-down resistor at any end. It is easy to be disturbed and oscillated when turning the machine on and off, and in severe cases, it may cause the MOSFET to be mis-turned on.

[0039] The present application proposes to add a pull-down circuit near the output end of the bus transceiver and the input end of the driving circuit for the power device, so as to realize reliable and rapid shutdown of the driving signal.

[0040] Please refer to Figure 1 , shows a schematic diagram of an overcurrent protection circuit 120 of an embodiment. The overcurrent protection circuit 120 includes a current sampling circuit 121, a comparator circuit 122, a bus transceiver circuit 123, a drive circuit 124, a first pull-down circuit 125, and a second pull-down circuit 126. The overcurrent protection circuit 120 can monitor the current in the DC-DC converter 110, and when an overcurrent occurs, quickly and reliably shut down the drive signal provided to the DC-DC converter 110, thereby realizing the protection function of the power device (e.g., MOSFET) in the DC-DC converter 110. Figure 1 In the figure, the dotted line in the connection line between the bus transceiver circuit 123 and the driving circuit 124 indicates that the connection line between the two components can be longer.

[0041] The current sampling circuit 121 may include a coupling terminal and an output terminal, and is coupled to the DC-DC converter 110 through its coupling terminal for current sampling of the DC-DC converter 110, and is connected to the comparator circuit 122 through its output terminal and outputs a sampling voltage signal to the comparator circuit 122. In some embodiments, when an overcurrent occurs in the DC-DC converter 110, the sampling voltage signal may increase in a positive correlation and exceed a certain level.

[0042] The comparator circuit 122 may include a first input terminal, a second input terminal, and an output terminal. The comparator circuit 122 may be connected to the output terminal of the current sampling circuit 121 through its first input terminal to receive a sampled voltage signal, receive a reference voltage through its second input terminal, and compare the sampled voltage signal with the reference voltage to output a comparison voltage signal through its output terminal. In some embodiments, when the sampled voltage signal is less than the reference voltage signal, the comparator circuit 122 may output a low-level comparison voltage signal, and when the sampled voltage signal is greater than the reference voltage signal, the comparator circuit 122 may output a high-level comparison voltage signal.

[0043] The bus transceiver circuit 123 may include a control terminal and an output terminal. The bus transceiver circuit 123 may be connected to the output terminal of the comparator circuit 122 through its control terminal to receive a comparison voltage signal, and may output a drive signal to the drive circuit 124 through its output terminal in response to the comparison voltage signal, or cause its output terminal to stop outputting the drive signal and be in a high impedance state. In addition, as is well known to those skilled in the art, the bus transceiver circuit 123 may also isolate the power supply from the signal and perform level conversion on the input signal and the output signal, but these contents are not the focus of this article and will not be repeated here.

[0044] The drive circuit 124 may include an input end and an output end. The drive circuit 124 may be connected to the output end of the bus transceiver circuit 123 through its input end to receive and transform the drive signal, and provide the transformed drive signal to the switch tube in the DC-DC converter through its output end. In addition, the drive circuit 124 may isolate the input signal from the output signal and amplify the power.

[0045] The first pull-down circuit 125 may include a first end and a second end. The first pull-down circuit 125 may be connected to the proximal end of the output end of the bus transceiver circuit 123 through its first end, and grounded through its second end. When the output end of the bus transceiver circuit 123 stops outputting the driving signal, it may be in a high impedance state. By accessing the first pull-down circuit 125, the output signal of the bus transceiver circuit 123 may be quickly changed to a low level state.

[0046] The second pull-down circuit 126 may include a first end and a second end. The second pull-down circuit 126 may be connected to the proximal end of the input end of the driving circuit 124 through its first end, and grounded through its second end. Since the connection line between the bus transceiver circuit 123 and the driving circuit 124 is usually long, the driving signal is more susceptible to external interference. By adding the second pull-down circuit 126, when the bus transceiver circuit 123 stops outputting the driving signal, the input end of the driving circuit 124 can quickly stabilize to a low level state, thereby improving the anti-interference ability.

[0047] In some embodiments, the control terminal of the bus transceiver circuit 123 may be an enable terminal for controlling the output of the output terminal. In some embodiments, the enable terminal may enable the output terminal of the bus transceiver circuit 123 to output a driving signal when the comparison voltage signal is a low level signal, and may enable the output terminal of the bus transceiver circuit 123 to stop outputting the driving signal and maintain a high impedance state when the comparison voltage signal is a high level signal.

[0048] In some embodiments, the first pull-down circuit 125 and the second pull-down circuit 126 may include a pull-down resistor in the kilo-ohm range. In some embodiments, the first pull-down circuit 125 and the second pull-down circuit 126 may both be 1 kΩ pull-down resistors.

[0049] In some embodiments, bus transceiver circuit 123 may include a dual supply bus transceiver 245 chip.

[0050] See also Figure 2 , shows a top view of a dual power bus transceiver 245 chip 200 according to an embodiment. The chip 200 may include a power supply pin V CCA and two power supply pins V CCB , 8 input / output pins (i.e., A1-A8 and B1-B8), direction control pin DIR, enable pin and ground pin GND. The main function of chip 200 is to isolate the signal and power supply and to convert the input and output signals. CCA The power supply is 3.3V, and the input signal is also 3.3V; V CCB If the power supply is 5V, the output signal can be changed to 5V. The direction control pin DIR can control the direction of input and output. Enable pin The output terminal of the chip 200 can be controlled so that the output terminal outputs a driving signal or stops outputting a driving signal. The output pin of the chip 200 can be in a high impedance state.

[0051] It should be noted that the above dual-power bus transceiver 245 chip 200 is only an example, and those skilled in the art can conceive of applying the present application to other bus transceiver circuits.

[0052] In some embodiments, the DC-DC converter 110 may include a MOSFET tube. The driving signal output by the driving circuit 124 may be provided to the control electrode of the MOSFET tube, thereby controlling the on and off of the MOSFET tube, so that when an overcurrent occurs in the DC-DC converter 110, the MOSFET tube is quickly turned off, thereby avoiding the long-term on-state and thermal failure caused by the overcurrent, thereby playing a protective role.

[0053] The working principle of the overcurrent protection circuit 120 is specifically described below through the following embodiments. When there is no current overcurrent in the DC-DC converter 110, the sampling voltage signal output by the current sampling circuit 121 can be less than the reference voltage of the comparator circuit 122, and accordingly the comparator circuit 122 can provide a low-level comparison voltage signal to the enable end of the bus transceiver circuit 123, so that the bus transceiver circuit 123 can work normally and output a drive signal, and then the drive circuit 124 can receive the drive signal and transform it, and then provide a drive signal to the control electrode of the MOSFET tube in the DC-DC converter 110, so that it works normally and is in a conducting state, so that the DC-DC converter 110 can also work normally. However, when a current overcurrent occurs in the DC-DC converter 110, the sampling voltage signal can become greater than the reference voltage, so the comparator circuit 122 can output a high-level comparison voltage signal, and in response to the enable end of the bus transceiver circuit 123 receiving a high-level signal, the bus transceiver circuit 123 can stop outputting the drive signal and its output end can be in a high impedance state. Since the pull-down circuits are respectively connected to the output end of the bus transceiver circuit 123 and the input end of the driving circuit 124, the input end signal of the driving circuit 124 can be quickly stabilized to a low level state, so that the driving signal at its output end can be quickly blocked (i.e., shut down), and the MOSFET tube in the DC-DC converter 110 is also quickly shut down accordingly, thereby protecting the DC-DC converter 110.

[0054] In the above embodiment, since the output end of the bus transceiver circuit 123 is in a high impedance state, when the driving signal is turned off through the enable end and no pull-down resistor is added, in the process of the output end voltage of the bus transceiver circuit 123 changing from a high level to a low level, the voltage drops slowly until it drops to the threshold voltage of the input end of the driving circuit 124, and the output of the driving circuit 124 will become a low level, which will cause the switch tube (such as a MOSFET tube) in the DC-DC converter 110 to be continuously turned on for too long and the current is large, and the switch tube is prone to thermal failure. By adding the first pull-down circuit 125, in the process of the output end driving signal of the bus transceiver circuit 123 changing from a high level to a low level, the current is pulled to the ground through the first pull-down circuit 125, and the driving signal can be quickly stabilized to a low level state, and the output signal of the driving circuit 124 can also quickly drop to a low level at the same time to turn off the switch tube in the DC-DC converter 110.

[0055] In addition, in the above embodiments, only adding a pull-down circuit at the output end of the bus transceiver circuit 123 may not be able to quickly pull down the voltage level of the input end of the driving circuit 124, which may still cause the switch tube in the DC-DC converter 110 to be mis-conducted. However, by adding a second pull-down circuit 126 at the input end of the driving circuit 124, the driving signal at the input end can be quickly dropped to a stable low-level state. In addition, the connection line from the output end of the bus transceiver circuit 123 to the input end of the driving circuit 124 may usually be long, and the driving signal is more susceptible to external interference. By adding the second pull-down circuit 126, the anti-interference ability can be improved.

[0056] Therefore, in the above embodiment, by adding a pull-down circuit near the output end of the bus transceiver circuit 123 and the input end of the driving circuit 124, the problem of mis-conduction of the switch tube in the DC-DC converter 110 caused by the high impedance state of the output end of the bus transceiver circuit can be effectively solved, thereby realizing a reliable and fast current overcurrent protection function for the DC-DC converter 110.

[0057] See also Figure 3 , shows a circuit diagram of a current sampling circuit 310, a comparator circuit 320 and a dual power bus transceiver 245 chip circuit 330 in an overcurrent protection circuit of an embodiment.

[0058] In this embodiment, the current sampling circuit 310 may include a transformer CT, a bridge rectifier circuit 312 and a first resistor R1. The transformer CT reduces the current according to the required ratio, rectifies it through the rectifier circuit, and applies the rectified voltage to both ends of the first resistor R1 to calculate the current size, that is, I=U / R, wherein the transformer CT may be an AC current transformer. The transformer CT may be coupled with the transformer T1 of the DC-DC converter 340, and the transformer CT may include a first terminal CT1 and a second terminal CT2. The bridge rectifier circuit 312 may include a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4. The node between the anode of the first diode D1 and the cathode of the second diode D2 is used as the first input terminal, the node between the anode of the third diode D3 and the cathode of the fourth diode D4 is used as the second input terminal, the node between the cathode of the first diode D1 and the cathode of the third diode D3 is used as the positive output terminal, and the node between the anode of the second diode D2 and the anode of the fourth diode D4 is used as the negative output terminal. The first input terminal of the bridge rectifier circuit 312 can be connected to the first terminal CT1 of the transformer CT, the second input terminal thereof can be connected to the second terminal CT2 of the transformer CT, the positive output terminal thereof can be connected to one end of the first resistor R1, and the negative output terminal thereof can be connected to the other end of the first resistor R1 and to ground, where AGND represents analog ground.

[0059] The comparator circuit 320 may include a comparator chip, one input end of which may receive a reference voltage REF, and another input end of which may be connected to the positive output end of the bridge rectifier circuit 312 through a second resistor R2. In addition, the other input end of the comparator circuit 320 may also be grounded through a capacitor C1. The output end of the comparator circuit 320 may be connected to the enable end of the dual power bus transceiver 245 chip circuit 330. When the current sampling voltage is greater than the reference voltage REF, the comparator circuit 320 may output a high level, otherwise, it may output a low level.

[0060] The dual power bus transceiver 245 chip circuit 330 may include input pins A1-A8 and output pins B1-B8, as well as a power supply pin V CCA 、V CCB1 and V CCB2 . Power supply pin V CCA Can be connected to the power supply VDD, and the power supply pin V CCB1 and V CCB2It can be connected to another power supply VCC. Input pins A1 and A2 can receive pulse width modulation (PWM) signals PWM 1A and PWM 1B respectively. The dual power bus transceiver 245 chip circuit 330 can convert the levels of the two signals and output them through output pins B1 and B2 respectively. The output pins B1 and B2 can be grounded through the third resistor R1 and the fourth resistor R4 respectively, where DGND represents digital ground.

[0061] The DC-DC converter 340 may include a first MOSFET tube Q1, a second MOSFET tube Q2, capacitors C3 and C4, an inductor L1, and a transformer T1 constituting an LLC resonant circuit. The drain D of the first MOSFET tube Q1 may be connected to the first end of the capacitor C2 and the first end of the capacitor C3, respectively, the source S may be connected to the drain D of the second MOSFET tube Q2, and the node between the source S and the drain D may be connected to the first end of the transformer T1 through the inductor L1. The source S of the second MOSFET tube Q2 may be connected to the second end of the capacitor C2 and the second end of the capacitor C4, respectively. The second end of the capacitor C3 may be connected to the first end of the capacitor C4, and the node therebetween may be connected to the second end of the transformer T1. The gates G of the first MOSFET tube Q1 and the second MOSFET tube Q2 may receive the drive signals DRV_UP and DRV_DO, respectively, and be controlled on and off by them.

[0062] See also Figure 4 , shows a circuit diagram of a driving circuit 400 in an overcurrent protection circuit of an embodiment. The driving circuit 400 may include a driving chip U3 and peripheral circuits. The driving circuit 400 is used to isolate and power amplify the driving signals PWM 1A and PWM 1B.

[0063] The driver chip U3 may include input pins PWMH and PWML for receiving drive signals PWM 1A and PWM 1B, power supply pins VCC1 and VCC2, analog ground pin AGND, high-side and low-side gate pull-up pins HGP and LGP, high-side and low-side gate negative pins HGN and LGN, switch pin SW, bootstrap pin BST, power ground pin PGND, and reserved pins N / C and N / C / TP. The power supply pins VCC1 and VCC2 can be connected to the power supply VCC and grounded through capacitor C7. In addition, the power supply pins VCC1 and VCC2 can also be connected to the bootstrap pin BST through a diode D5. The bootstrap pin BST can be connected to the switch pin SW through a capacitor C8. The high-side gate pull-up pin HGP and the high-side gate negative pin HGN can be used to provide a drive signal DRV_UP, and the low-side gate pull-up pin LGP and the low-side gate negative pin LGN can be used to provide a drive signal DRV_DO.

[0064] The peripheral circuit may include capacitors C5 and C6. One end of the capacitors C5 and C6 may be connected to the input pins PWML and PWMH, respectively, and the other end may be grounded.

[0065] When the pull-down resistors R7 and R8 are connected to the input pins PWML and PWMH of the driver chip U3 respectively, the pull-down resistors R7 and R8 can quickly discharge the capacitors C5 and C6, so that the signals of the input pins PWML and PWMH are quickly stabilized to a low level state.

[0066] In this implementation, by adding pull-down resistors at the proximal end of the output end of the dual power bus transceiver 245 chip circuit and the proximal end of the input end of the driver chip U3, when a fault shutdown occurs or the drive signal is interfered with, the input end signal of the driver chip U3 can be quickly pulled down to a low level, thereby quickly blocking the drive signal output by the driver chip U3 and protecting the MOSFET tube in the DC-DC converter.

[0067] It should be pointed out that the above driver chip U3 is only an example, and those skilled in the art can easily think of applying the present application to other driver chips.

[0068] Figure 5 FIG. 5 is a block diagram of a DC-DC converter system 500 according to an embodiment. As shown in the figure, the DC-DC converter system 500 may include a DC-DC converter 501 and an overcurrent protection circuit 502 according to any of the above embodiments.

[0069] The above specific examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. For those skilled in the art of the present invention, some simple deductions, deformations or substitutions can be made based on the idea of ​​the present invention.

Claims

1. An overcurrent protection circuit for a DC-DC converter, characterized in that: include: A current sampling circuit, a comparator circuit, a bus transceiver circuit, a driving circuit, a first pull-down circuit, and a second pull-down circuit; The current sampling circuit comprises a coupling end and an output end, the current sampling circuit is coupled to the DC-DC converter through its coupling end to perform current sampling on the DC-DC converter, and outputs a first voltage signal through its output end; The comparator circuit comprises a first input terminal, a second input terminal and an output terminal. The comparator circuit is connected to the output terminal of the current sampling circuit through its first input terminal to receive the first voltage signal, receives a reference voltage signal through its second input terminal, compares the first voltage signal with the reference voltage signal and outputs a second voltage signal through its output terminal. The bus transceiver circuit comprises a control terminal and an output terminal, wherein the bus transceiver circuit is connected to the output terminal of the comparator circuit through the control terminal to receive the second voltage signal, and in response to the second voltage signal, outputs a driving signal through the output terminal or stops the output terminal from outputting the driving signal and is in a high impedance state; The driving circuit comprises an input end and an output end, wherein the driving circuit is connected to the output end of the bus transceiver circuit through its input end to receive and transform the driving signal, and provides the transformed driving signal to the switch tube in the DC-DC converter through its output end; The first pull-down circuit includes a first end and a second end, the first pull-down circuit is connected to the output end of the bus transceiver circuit through its first end and is grounded through its second end; The second pull-down circuit includes a first terminal and a second terminal, and the second pull-down circuit is connected to the input terminal of the driving circuit through the first terminal and is grounded through the second terminal.

2. The overcurrent protection circuit according to claim 1, characterized in that: When the first voltage signal is smaller than the reference voltage signal, the second voltage signal is a low level signal. When the first voltage signal is larger than the reference voltage signal, the second voltage signal is a high level signal.

3. The overcurrent protection circuit according to claim 1 or 2, characterized in that: The control end of the bus transceiver circuit includes an enable end. When the second voltage signal is a low-level signal, the enable end enables the output end of the bus transceiver circuit to output the drive signal. When the second voltage signal is a high-level signal, the enable end enables the output end of the bus transceiver circuit to stop outputting the drive signal and be in a high-impedance state.

4. The overcurrent protection circuit according to claim 1, characterized in that: The DC-DC converter includes a transformer, the coupling end of the current sampling circuit includes a mutual inductor, the mutual inductor is coupled to the transformer, and the mutual inductor includes a first end and a second end; The current sampling circuit also includes a bridge rectifier circuit and a first resistor; The first resistor includes a first end and a second end; The bridge rectifier circuit comprises a first diode, a second diode, a third diode and a fourth diode connected in a bridge manner, a node between an anode of the first diode and a cathode of the second diode serving as a first input terminal, a node between an anode of the third diode and a cathode of the fourth diode serving as a second input terminal, a node between a cathode of the first diode and a cathode of the third diode serving as a positive output terminal, and a node between an anode of the second diode and an anode of the fourth diode serving as a negative output terminal; The bridge rectifier circuit is connected to the first end of the mutual inductor through its first input end, connected to the second end of the mutual inductor through its second input end, connected to the first end of the first resistor through its positive output end, and connected to the second end of the first resistor and grounded through its negative output end; The positive output terminal of the bridge rectifier circuit is connected to the first input terminal of the comparator circuit as the output terminal of the current sampling circuit.

5. The overcurrent protection circuit according to claim 1, characterized in that: The driving circuit includes a driving chip and a peripheral circuit. The driving chip includes an input terminal and an output terminal, and is connected to the input terminal of the driving circuit through its input terminal and to the output terminal of the driving circuit through its output terminal. The peripheral circuit includes a capacitor. The capacitor includes a first terminal and a second terminal. The capacitor is connected to the input terminal of the driving chip through its first terminal and is grounded through its second terminal.

6. The overcurrent protection circuit according to claim 1, characterized in that: The first pull-down circuit and the second pull-down circuit each include a pull-down resistor in the kilo-ohm range.

7. The overcurrent protection circuit according to claim 1, characterized in that: The bus transceiver circuit includes a dual power bus transceiver 245 chip circuit.

8. The overcurrent protection circuit according to claim 1, characterized in that: The switch tube in the DC-DC converter includes a MOSFET tube, and the converted drive signal is provided to the control electrode of the MOSFET tube.

9. The overcurrent protection circuit according to claim 1, characterized in that: The driving signal includes a pulse width modulation signal.

10. A DC-DC converter system, characterized in that: The invention comprises a DC-DC converter and an overcurrent protection circuit according to any one of claims 1 to 9.

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