A power tube driving protection circuit

Abstract

The application discloses a power transistor driving protection circuit, which comprises a low-voltage driving circuit, a power enhancement unit, a circuit protection unit, a power transistor and a power supply. The low-voltage driving circuit receives a control signal and outputs the signal, the signal enters the power enhancement unit, is amplified into a power signal with driving capacity, the power signal sequentially passes through a fuse and a resistor, and is then transmitted to the power transistor, so that the conduction, shutdown or opening degree of the power transistor in the next stage is controlled according to the signal instruction, and the circuit protection unit comprises a clamping diode and a fuse, the clamping diode performs clamping protection on the circuit voltage, and the fuse starts protection when overcurrent occurs. The circuit of the application increases a protection circuit between the output of the low-voltage side driving circuit and the transistor control pin. When the transistor fails, high voltage can be effectively avoided from entering the low-voltage circuit, the impact of high voltage on the driving related circuit is prevented, meanwhile, damage can be isolated, and associated damage is prevented.

Description

Technical Field

[0001] This invention relates to the field of integrated circuit technology, and more specifically to a power transistor drive protection circuit. Background Technology

[0002] The power sections of power electronic devices typically consist of various transistors. To meet market demands for higher power, more transistors are usually connected in parallel to handle greater power. These power transistors are usually equipped with their own low-voltage drive circuits.

[0003] As market demands for power and voltage in power electronic devices increase, power transistors are subjected to higher temperatures and electrical stresses. Under prolonged high-stress operating conditions, transistor lifespan decreases, leading to failure. When a transistor fails, it impacts its low-voltage drive circuit. Especially under high-voltage conditions, the high voltage may interfere with the low-voltage control circuit, causing overvoltage damage. This, in turn, affects other undamaged transistor circuits, causing them to fail as well, creating a vicious cycle and resulting in damage to more and larger areas of devices. In extreme cases, this could even lead to serious accidents such as fires. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to address the shortcomings of existing technologies by designing a power transistor drive protection circuit. The circuit proposed in this invention protects the low-voltage drive circuit when a single local power transistor is damaged, preventing further cascading damage and effectively avoiding the spread of damage.

[0005] This invention discloses a power transistor drive protection circuit, comprising: a low-voltage drive circuit, a power enhancement unit, a circuit protection unit, a power transistor, and a power supply. The low-voltage drive circuit is used to receive weak control signals and convert them into low-voltage drive signals adapted to subsequent circuits, serving as the signal input terminal for the entire circuit. The power enhancement unit amplifies the signal output from the low-voltage drive circuit, and the output signal of the power enhancement unit controls the conduction, turn-off, or on degree of the subsequent power transistor. The circuit protection unit includes a second clamping diode, a first fuse, and a second fuse. The first fuse and the second fuse are connected in series between the power enhancement unit and the power transistor control terminal. One end of the second clamping diode is connected to the connection terminal of the first fuse and the second fuse, and the other end is connected to the power ground.

[0006] Furthermore, a first clamping diode is connected to ground between the low-voltage drive circuit and the power enhancement unit.

[0007] Furthermore, the power enhancement unit is an operational amplifier circuit with driving capability or a push-pull circuit composed of transistors.

[0008] Furthermore, a high-voltage reverse bias diode is connected in series at the power input terminal of the power enhancement unit.

[0009] The beneficial effects of the technical solution of this invention are as follows: by adding a circuit protection unit between the low-voltage drive circuit and the power transistor, when the power transistor fails, it can simply and effectively prevent high voltage from entering the voltage control side circuit, prevent high voltage from impacting the drive-related circuit and causing cascading damage, and at the same time effectively prevent the damage from spreading and thus damaging the core components. Attached Figure Description

[0010] Figure 1 This is a schematic diagram of the overall framework of the present invention.

[0011] Figure 2 This is a schematic diagram illustrating the working principle of the power transistor drive protection circuit of the present invention. Detailed Implementation

[0012] The technical solution of the present invention will be described in detail below, but the scope of protection of the present invention is not limited to the embodiments described.

[0013] like Figure 1 As shown, this invention discloses a power transistor drive and protection circuit, comprising: a low-voltage drive circuit, a power enhancement unit, a circuit protection unit, a power transistor, and a power supply. The low-voltage drive circuit and the power enhancement unit serve as system input terminals, responsible for low-voltage drive and power amplification of weak signals, providing sufficiently strong control signals for subsequent circuits. The circuit protection unit is connected in series between the low-voltage drive circuit and the power transistor, capable of detecting and protecting against abnormal operating conditions such as overcurrent, overvoltage, and overheating, preventing damage to the core power device. The power transistor, as the core actuator of the system, controls the conduction, turn-off, or on-state of the subsequent power transistor based on the output signal of the power enhancement unit. The power supply provides operating power for the entire circuit system and simultaneously provides energy support for the high-power output of the power transistor.

[0014] The specific working principle is as follows: Figure 2As shown, in a power transistor drive protection circuit disclosed in this invention, the circuit protection unit includes a second clamping diode D3, a first fuse F1, and a second fuse F2. The second clamping diode D3 is a bidirectional Zener diode, capable of clamping and protecting against overvoltage and reverse voltage in the circuit, preventing damage to the power transistor due to abnormal voltage. When an overcurrent fault occurs in the circuit, the first fuse F1 and the second fuse F2 blow, cutting off the circuit and preventing the fault from escalating and damaging core components. The output terminal of the low-voltage drive circuit is connected to the input terminal of the power enhancement unit, and the first clamping diode D2 is connected to the power supply ground between the low-voltage drive circuit and the power enhancement unit. During normal operation, the first clamping diode D2 is in a reverse cutoff state, not affecting the transmission of the low-voltage drive signal; when the power transistor Q1 malfunctions and high voltage flows into the low-voltage drive circuit through the power enhancement unit in reverse, the first clamping diode D2 will momentarily conduct in the forward direction, clamping the incoming high voltage within a safe voltage range, while simultaneously discharging the overload current to the power supply ground, preventing the chips and components of the low-voltage drive circuit from being damaged by high voltage. The power enhancement unit can be an operational amplifier circuit with driving capability or a push-pull circuit composed of transistors. The power enhancement unit is connected to a VC power supply, which is the internal low-voltage side power supply. This power supply provides unidirectional power to the power enhancement unit through a series high-voltage reverse-biased diode D1. During normal operation, the high-voltage reverse-biased diode D1 conducts in the forward direction, providing the VC low-voltage power supply to the power enhancement unit. When the power transistor Q1 fails, and high voltage flows into the power enhancement unit in the reverse direction, the high-voltage reverse-biased diode D1 will reverse-bias, completely cutting off the conduction path from the high voltage to the low-voltage power supply system, preventing the VC power supply from being damaged by high voltage breakdown. The output of the power enhancement unit is connected to the control pin of the power transistor Q1 through a series connection of a second fuse F2, a first fuse F1, and a resistor R1. Simultaneously, a second clamping diode D3 is connected between the lead connecting the second fuse F2 and the first fuse F1 and the power supply ground. During normal operation, the second clamping diode D3 is reverse-biased and cut off, ensuring that the control signal is transmitted to the control pin of power transistor Q1 via the first fuse F1, the second fuse F2, and resistor R1. When power transistor Q1 fails and a high voltage far exceeding its rated value is applied to the control pin, the second clamping diode D3 will conduct bidirectionally (bidirectional TVS characteristic), clamping the voltage at the connection between the first fuse F1 and the second fuse F2 to a safe value. Simultaneously, it discharges the large current to ground, serving as dedicated voltage protection for power transistor Q1 to prevent its control pin from being damaged by high voltage. Furthermore, the large current will trigger the first fuse F1 to blow, cutting off the fault circuit. Resistor R1 is typically a damping resistor for the control terminal of power transistor Q1 to prevent high-frequency oscillation. The two external terminals of power transistor Q1 are connected to the power supply. Power transistor Q1 can be a metal-oxide-semiconductor field-effect transistor, a power transistor, an IGBT, etc. The first clamping diode D2 and the second clamping diode D3 can be overvoltage protection devices such as Zener diodes, TVS diodes, or varistors.

[0015] When the circuit is operating normally, neither the first clamping diode D2 nor the second clamping diode D3 is active. The output of the low-voltage drive circuit, after power amplification, is applied to the control terminal of the power transistor Q1 through fuses F1 and F2. This is consistent with the normal operating state without protection. When the power transistor Q1 fails, a relatively high voltage, far exceeding the low-voltage side supply voltage, is introduced into its control pin. First, the second clamping diode D3 activates, clamping the voltage at the connection point of the first fuse F1 and the second fuse F2 to prevent excessive voltage. At this time, a very high current flows through the second clamping diode D3 to ground. This high current flows through the first fuse F1, exceeding its fusing current, causing the first fuse F1 to open, thus cutting off the high voltage. Sometimes, when the power transistor Q1 fails, the energy introduced into the control terminal is too high, and the second clamping diode D3, with its limited absorption capacity, may also fail. In this case, the second fuse F2 and the power amplification unit can further absorb the high voltage energy, preventing it from further propagating into the low-voltage control circuit. The power supply for the power enhancement unit is introduced through a high-voltage reverse bias diode D1. Even if the power enhancement unit fails to absorb high-voltage energy and is damaged, the high-voltage reverse bias diode D1 prevents energy from entering the power supply system. Similarly, a first clamping diode D2 is located between the output of the low-voltage drive circuit and the power supply ground, protecting the low-voltage circuit from high-voltage intrusion. Furthermore, the second fuse F2 serves two purposes: firstly, when residual high-voltage energy from the outside enters, it can exceed the current limit and blow the fuse in conjunction with a short circuit in the power enhancement unit, cutting off the high-voltage circuit. In some cases, if the second clamping diode D3 fails and short-circuits, the first fuse F1 will blow. At this time, the output current of the power enhancement unit flows through the second fuse F2 to the damaged second clamping diode D3 and then to the power supply ground. Secondly, this short-circuit current can also cause the second fuse F2 to blow, cutting off the loop from the power enhancement unit to the second clamping diode D3 and preventing the short circuit of the second clamping diode D3 from affecting the system power supply VC.

[0016] This invention discloses a power transistor drive protection circuit that achieves layered protection when high-voltage crosstalk is caused by the failure of power transistor Q1 through a three-level cooperative mechanism of "clamping-fuse-isolation". The first fuse F1 and the second fuse F2 form a "double break point". Even if the second clamping diode D3 is short-circuited and the first fuse F1 blows, the second fuse F2 can still independently cut off the secondary fault circuit, achieving double isolation of the fault path.

[0017] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A power transistor drive protection circuit, characterized in that, include: Low-voltage drive circuit, power enhancement unit, circuit protection unit, power transistor and power supply, The low-voltage drive circuit is used to receive weak control signals and convert them into low-voltage drive signals adapted to subsequent circuits, serving as the signal input terminal for the entire circuit. The power enhancement unit amplifies the signal output from the low-voltage drive circuit, and the output signal of the power enhancement unit controls the conduction, turn-off, or on degree of the subsequent power transistor. The circuit protection unit includes a second clamping diode, a first fuse, and a second fuse. The first fuse and the second fuse are connected in series between the power enhancement unit and the power transistor control terminal. One end of the second clamping diode is connected to the connection terminal of the first fuse and the second fuse, and the other end is connected to the power ground.

2. The power transistor drive protection circuit according to claim 1, characterized in that, The low-voltage drive circuit and the power enhancement unit are connected to ground via a first clamping diode.

3. The power transistor drive protection circuit according to claim 1, characterized in that, The power enhancement unit is an operational amplifier circuit with driving capability or a push-pull circuit composed of transistors.

4. The power transistor drive protection circuit according to claim 1, characterized in that, A high-voltage reverse-biased diode is connected in series at the power input terminal of the power enhancement unit.

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