A topology of over-current protection circuit based on DC-DC converter

Abstract

The utility model discloses a kind of overcurrent protection circuit topological structures based on DC-DC converter, and overcurrent protection circuit is equipped with delay protection chip, and the chip is equipped with undervoltage threshold detection unit and delay reset unit.The voltage signal of sampling resistance is connected with the detection pin of the delay protection chip by double operational amplifier.The one pin of the delay protection chip is connected with two parallel capacitors.Delay protection chip uses BU4225G-TR chip.When power voltage is lower than threshold value, chip will not immediately output reset signal, but output after a adjustable delay time.This can avoid false reset due to the temporary fluctuation of power voltage, and improve the stability of system.

Description

Technical Field

[0001] This utility model relates to a switching converter, and more particularly to an overcurrent protection circuit topology based on a DC-DC converter. Background Technology

[0002] Since the advent of switching converters, their various topologies and operating mechanisms have been a hot research topic for many researchers. The study of DC-DC converters is particularly crucial in achieving high-frequency, high-efficiency, and modular switching power supplies. DC-DC converters are classified into two types based on whether they have electrical isolation: isolated converters, where the input and output are electrically isolated through components such as transformers, achieving high safety and anti-interference characteristics; and non-isolated converters, which typically lack transformers and other magnetic components, resulting in a relatively smaller number of components and reduced energy loss between components, especially avoiding transformer core losses and winding resistance losses. For example, in some simple buck or boost non-isolated converters, the circuit structure is simple, the energy conversion process is more direct, and the conversion efficiency is higher. However, because there is no electrical isolation between the input and output, when a circuit fault occurs (such as an accidental connection between the high-voltage section on the input side and the low-voltage section on the output side), the output may carry a dangerously high voltage. If a user unknowingly touches the output of a non-isolated converter, there is a risk of electric shock, which is a very serious problem in applications with high human safety requirements (such as home electronics and medical equipment). DC-DC circuit protection strategies include overvoltage protection (OVP), undervoltage protection (UVP), overheat protection (OTP), short circuit protection, overcurrent protection (OCP), as well as load drop protection, reverse polarity protection, and high voltage safety protection in the automotive electronics field (not listed), grid connection protection in the new energy field, leakage current protection and grounding protection in the medical electronics field, and radiation protection in the aerospace field.

[0003] Common isolated DC-DC converters include forward, flyback, half-bridge, full-bridge, and push-pull types. Another type is the non-isolated DC-DC converter, which has no electrical isolation between its input and output. It has a relatively simple circuit structure, lower cost, and higher efficiency. Common non-isolated DC-DC converters include buck, boost, Cuk, Zeta, and Sepic types. Overvoltage protection (OVP) activates when the output voltage of the DC-DC converter exceeds a specified upper limit to prevent damage to the load connected to the output terminal. Undervoltage protection (UVP) activates when the output voltage of the DC-DC converter falls below a set lower limit, indicating an undervoltage condition, to prevent the load device from malfunctioning or being damaged due to insufficient voltage. Overheat protection (OTP) is necessary because DC-DC converters generate heat during operation; poor heat dissipation or abnormal operating conditions can lead to overheating. Overheat protection aims to prevent converter damage due to overheating by taking timely measures when the temperature exceeds the safe range. Overcurrent protection (OCP) is a protection mechanism triggered when the output current of the DC-DC converter exceeds a preset safe threshold. This is to prevent excessive current from damaging components in the circuit, such as power switches, inductors, and capacitors. Overcurrent protection is divided into two types: one is hardware detection, which monitors the current using current sensors (such as Hall effect sensors or sampling resistors). When the current value detected by the sensor exceeds the set value, a signal is generated by a comparator or other circuits, triggering the protection circuit to act, for example, cutting off the drive signal of the power switch and stopping the converter. The other type is software detection, which uses software algorithms to monitor and analyze the current in real time. When an abnormal current is detected, the software controls the relevant circuits to act, realizing overcurrent protection.

[0004] Existing technology

[0005] like Figure 1 As shown, the forward converter is the most commonly used topology in current switching power supply design. A forward converter circuit can be broken down into: input power supply, switching devices (such as transistors, IGBTs, etc.), transformer, rectifier diodes, filter capacitors, and load. Among these, the switching devices are the core components controlling the on / off state of the circuit; the transformer provides electrical isolation and voltage transformation between input and output; the rectifier diodes convert the AC output from the transformer's secondary winding into DC; and the filter capacitors smooth the output voltage and reduce voltage ripple. Its advantages include good output characteristics, a wide power range, and relatively simple circuitry.

[0006] Disadvantages of existing technology:

[0007] In some semiconductor industries, robotic arms and DC motors are commonly used. These types of devices have low operating current during normal operation, but require a large starting current. Typically, the starting current can be 5 to 7 times the rated current. Therefore, traditional overcurrent protection circuit designs in forward converters cannot meet the requirements of such high starting current devices.

[0008] In view of the above, this utility model is hereby proposed. Utility Model Content

[0009] The purpose of this invention is to provide an overcurrent protection circuit topology based on a DC-DC converter to solve the aforementioned technical problems in the prior art.

[0010] The objective of this utility model is achieved through the following technical solution:

[0011] The present invention discloses an overcurrent protection circuit topology based on a DC-DC converter. The overcurrent protection circuit is equipped with a delay protection chip, which includes an undervoltage threshold detection unit and a delay reset unit.

[0012] Compared with existing technologies, the overcurrent protection circuit topology based on a DC-DC converter provided by this invention does not immediately output a reset signal when the power supply voltage is lower than the threshold. Instead, it outputs the signal after an adjustable delay. This avoids false resets caused by short-term fluctuations in the power supply voltage, thus improving system stability. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the topology of a two-transistor forward converter circuit in the prior art.

[0014] Figure 2 A schematic diagram of the overcurrent protection circuit topology based on a DC-DC converter provided for an embodiment of this utility model.

[0015] Figure 3 This is an internal block diagram of the power supply based on a forward converter according to an embodiment of the present invention. Detailed Implementation

[0016] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments, which do not constitute a limitation on the present utility model. Based on the embodiments of the present utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present utility model.

[0017] The contents not described in detail in the embodiments of this utility model are existing technologies known to those skilled in the art. Where specific conditions are not specified in the embodiments of this utility model, they shall be performed according to conventional conditions in the art or conditions recommended by the manufacturer. Reagents or instruments used in the embodiments of this utility model whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0018] This utility model discloses an overcurrent protection circuit topology based on a DC-DC converter. The overcurrent protection circuit is equipped with a delay protection chip, which includes an undervoltage threshold detection unit and a delay reset unit.

[0019] The voltage signal of the sampling resistor is connected to the detection pin of the delay protection chip through a dual operational amplifier.

[0020] One pin of the delay protection chip is connected to two parallel capacitors.

[0021] The delay protection chip is a BU4225G-TR chip.

[0022] In summary, the overcurrent protection circuit topology based on a DC-DC converter in this embodiment of the invention does not immediately output a reset signal when the power supply voltage is below a threshold. Instead, it outputs the signal after an adjustable delay. This avoids false resets caused by short-term fluctuations in the power supply voltage, thus improving system stability.

[0023] To more clearly demonstrate the technical solution and its effects provided by this utility model, the embodiments of this utility model will be described in detail below with reference to specific examples.

[0024] Example 1

[0025] Specific circuit design such as Figure 2 As shown:

[0026] The BU4225G-TR chip provides a novel overcurrent protection strategy. First, the voltage signal acquired by the sampling resistor is amplified using dual operational amplifiers. This amplified signal is then connected to the chip's detection pin, where an undervoltage detection threshold is internally set. When the detected power supply voltage falls below this threshold, the chip determines an anomaly and enters an appropriate processing state. The BU4225G-TR chip also features a delayed reset function. When the power supply voltage drops below the threshold, the chip does not immediately output a reset signal but waits for an adjustable delay. This avoids false resets caused by brief fluctuations in the power supply voltage, improving system stability.

[0027] The specific delay time is determined by the capacitor connected to pin 5 of the chip.

[0028] Traditional forward converter-based switching power supplies include overcurrent, overvoltage, and short-circuit protection circuits. However, overcurrent protection circuits typically only consider constant current protection, meaning that when the current exceeds a set threshold, the protection function is activated, cutting off the converter output to protect downstream devices. However, some special applications require both stable power output and small size with high power density, especially in devices with motor loads. It's difficult to meet the high current demands during startup, or meeting them would trigger the overcurrent protection function, rendering the power supply unusable.

[0029] This invention adds a time-delay protection chip to the traditional overcurrent protection circuit design, which does not affect the performance of the power supply based on the forward converter and expands the application scenarios of the power supply to meet the needs of different devices.

[0030] Internal block diagram of a power supply based on a forward converter, such as... Figure 3 As shown.

[0031] The pre-amplifier PFC converter circuit uses a conventional booster to convert the single-phase input voltage of 180Vac to 264Vac into a stable 380Vdc. The post-amplifier uses a forward converter circuit to provide relatively large power output. When the switching transistor is turned on, the secondary coil of the transformer provides power output to the load, ensuring that the output voltage amplitude is basically stable. At the same time, the presence of the transformer provides electrical isolation between the input and output, improving the safety and reliability of the circuit and effectively preventing interference on the input side from affecting the output side.

[0032] In this utility model, the most frequently occurring component in the PFC circuit failures and quality issues is the power switching transistor (MOSFET). This solution is based on the existing and relatively mature power management chip-controlled PFC circuit, which is optimized by providing power transistor temperature monitoring to reduce the probability of this component failure. Simultaneously, it detects high and low levels to control PFC power supply, disconnects the thermistor to reduce losses, and ultimately provides protection for reliable PFC operation.

[0033] Key technical points of this utility model:

[0034] This utility model mainly designs a time-delay overcurrent protection circuit based on a forward converter topology, providing a high-power, high-efficiency switching power supply design solution. The key technical points are the selection of the delay chip, reasonable delay settings, and a reliable triggering mechanism.

[0035] The above description is merely a preferred embodiment of this utility model, but the scope of protection of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this utility model should be included within the scope of protection of this utility model. Therefore, the scope of protection of this utility model should be determined by the scope of the claims. The information disclosed in the background section is intended only to enhance the understanding of the overall background technology of this utility model and should not be construed as an admission or implication in any way that such information constitutes prior art known to those skilled in the art.

Claims

1. A topology of overcurrent protection circuit based on DC-DC converter, characterized in that, The overcurrent protection circuit is equipped with a delay protection chip, which includes an undervoltage threshold detection unit and a delay reset unit.

2. The overcurrent protection circuit topology based on a DC-DC converter according to claim 1, characterized in that, The voltage signal of the sampling resistor is connected to the detection pin of the delay protection chip through a dual operational amplifier.

3. The overcurrent protection circuit topology based on a DC-DC converter according to claim 2, characterized in that, One pin of the delay protection chip is connected to two parallel capacitors.

4. The overcurrent protection circuit topology based on a DC-DC converter according to claim 1, 2 or 3, characterized in that, The delay protection chip is a BU4225G-TR chip.

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