A variable conduction region MCT parallel current sharing circuit

Abstract

This invention belongs to the field of power semiconductor technology and relates to a parallel current sharing circuit for a variable conduction region MCT. This invention employs a gate layout partitioning and threshold hierarchical control method, dividing the MCT gate layout into multiple conduction regions. By combining a gate drive circuit, a pulse discharge circuit, a feedback circuit, and a gate control circuit, the MCT gate conduction regions are controlled in real time, achieving precise control of the current peak during pulse discharge. The gate drive circuit is powered by an external low-voltage power supply and provides the gate drive signal to the gate control circuit through a driver chip. The pulse discharge circuit is powered by an external high-voltage source, discharging a resistor to generate a high-frequency pulse current signal. The feedback circuit samples the current peak of the high-frequency pulse current signal and provides a feedback signal to the gate control circuit. The feedback signal from the feedback circuit is used to precisely control the MCT conduction regions. The parallel current sharing structure of the variable conduction region MCT has the advantages of high integration, small size, and high stability.

Description

Technical Field

[0001] This invention belongs to the field of power semiconductor technology and relates to a variable conduction region MCT parallel current sharing circuit. Background Technology

[0002] Pulsed power technology is an electrophysical method that stores energy in milliseconds and releases it in nanoseconds: the energy storage network first accumulates electrical energy over a relatively long time window, and then a high-speed switch delivers the energy to the load in an extremely short time, thereby achieving instantaneous power output in the megawatt to gigawatt range. With the maturity of power technology and the emergence of new demands, this technology has expanded from early defense applications such as pulsed strong magnetic fields, nuclear fusion ignition, and electromagnetic launch to civilian applications such as wastewater treatment, EUV lithography, high-power microwaves, and medical accelerators.

[0003] In pulsed power chains, switching devices are the core of energy storage-discharge switching, and they must simultaneously meet the comprehensive requirements of high withstand voltage (kilovolts), high pulse current (kiloamperes to megaamperes), high di / dt (>1 kA / μs), and high repetition frequency (kHz level). Traditional gas switches such as spark gaps, ignition tubes, and thyristors are no longer suitable for the trend of compact, high-frequency, and solid-state development due to their large trigger delay, complex drive, and bulky size. While semiconductor devices such as power MOSFETs, IGBTs, SCRs, and GTOs have advantages such as low cost, fast switching speed, and easy integration, they still have challenges such as slow frequency response and single-tube power limits that need to be overcome.

[0004] However, as the system's demand for pulse energy continues to rise, single devices can no longer meet the higher power levels. Compared to developing entirely new high-power devices, paralleling low-power MCTs for capacity expansion not only has a shorter development cycle and lower cost, but also offers greater engineering flexibility.

[0005] However, parallel topologies face the challenge of current uniformity: unavoidable parasitic differences (capacitance, resistance, inductance) between branches will cause an imbalance in pulse current distribution. In extreme cases, the power dissipation caused by branch overcurrent can cause a sudden rise in MCT junction temperature, inducing thermal breakdown and failure. Therefore, achieving parallel current sharing has become a key technical bottleneck for MCT power expansion. Summary of the Invention

[0006] The purpose of this invention is to address the aforementioned problems by proposing a parallel current-sharing structure for a variable conduction region MCT. This invention employs a cathode-shorted MOS-controlled thyristor (CS-MCT), combining the gate control simplicity of a MOSFET with the surge current capability of a thyristor, enabling the output of kiloampere-level pulse current while maintaining high di / dt. This invention solves the current distribution and thermal breakdown problems at the device level in one go, offering advantages such as high integration, high reliability, and easy scalability. Utilizing the strong surge capability and low conduction loss of the MCT device, this invention achieves a parallel current-sharing structure with programmable conduction region (1→n), linearly adjustable pulse current peak value, and automatic branch current balancing through two methods: gate layout partitioning and threshold hierarchical control.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A variable conduction region MCT parallel current sharing circuit includes a gate driving circuit, a pulse discharge circuit, a feedback circuit, and a gate control circuit.

[0009] The gate drive circuit is powered by an external low-voltage power supply and outputs a pulsed gate voltage signal to the gate control circuit.

[0010] The pulse discharge circuit includes a high-voltage capacitor, a resistor, and a variable conduction section (MCT). The pulse discharge circuit is powered by an external high-voltage power supply, which charges the high-voltage capacitor. The high-voltage capacitor, resistor, and MCT are connected to form a discharge circuit. When the MCT is in the blocking state, the voltage of the external high-voltage source is fully applied across the high-voltage capacitor. When the MCT is in the opening state, the high-voltage capacitor discharges to the resistor through the discharge circuit via a damped oscillation method, generating a high-pulse current output.

[0011] The feedback circuit samples the pulse discharge current of the discharge circuit, compares the peak value of the pulse current of the discharge circuit, and provides a feedback signal for the gate control circuit.

[0012] The gate control circuit controls the conduction region of the variable conduction region MCT under the combined action of the pulse gate voltage signal and the feedback signal, and determines whether each zone is turned on or off.

[0013] The variable conduction region (MCT) is implemented by dividing the MCT into multiple regions, one of which is a fixed normally-on region, while the others are variable conduction regions. Specifically, the MCT is isolated into multiple regions using an insulating dielectric material. Strip-shaped polysilicon gates are deposited on the N-wells and P-wells within each region. The polysilicon gates within the same region are interconnected, while the polysilicon gates in different regions are separated by the insulating dielectric material. In regions where the polysilicon gate voltage exceeds the threshold voltage, strong inversion occurs on the P-well surface, forming an electron channel. The anode and cathode at both ends of the partition are conductive, allowing pulse current to flow. Conversely, when the gate voltage is below the threshold, the corresponding region maintains high impedance, and the current is blocked. The normally-on region is always powered by the drive circuit and is used to release energy from the high-voltage capacitor in the pulse discharge circuit to establish a reference pulse current. The gate voltage of the remaining variable conduction regions is independently generated by the gate control circuit.

[0014] Furthermore, the method by which the gate control circuit controls the variable conduction region of the variable conduction region MCT is to preset a threshold voltage signal V for each variable conduction region of the variable conduction region MCT in the gate control circuit. Fn , where n is the variable conduction region number, n=1, 2, …; the feedback signal is defined as V. Feedback When V Feedback < V Fn When V is active, the corresponding variable conduction region and normally active region are turned on synchronously, and the conduction region is provided with the same gate drive signal by the gate drive circuit; when V Feedback ≥ V Fn When the variable conduction region is turned on, the gate is grounded and the gate voltage is forced to zero. When the variable conduction region is turned on, the peak value of the pulse current in the discharge circuit is compensated and increased. When the variable conduction region is turned off, the peak value of the pulse current in the discharge circuit decreases.

[0015] Furthermore, the variable conduction region MCT is a MOS-controlled thyristor with a cathode short-circuit structure. When the cathode is short-circuited to ensure that the gate voltage is zero, the device maintains high voltage blocking. After being turned on, it relies on the thyristor structure to provide high di / dt and high pulse current peak value.

[0016] The beneficial effects of this invention are as follows: This invention employs a gate layout partitioning and threshold hierarchical control method, dividing the MCT gate layout into multiple conduction regions. Combined with a gate drive circuit, pulse discharge circuit, feedback circuit, and gate control circuit, it achieves real-time control of the MCT gate conduction regions, realizing precise control of the current peak during pulse discharge. The gate drive circuit is powered by an external low-voltage power supply and provides the gate drive signal to the gate control circuit through a driver chip. The pulse discharge circuit is powered by an external high-voltage source, discharging the resistor to generate a high-frequency pulse current signal. The feedback circuit samples the current peak of the high-frequency pulse current signal and provides a feedback signal to the gate control circuit. The feedback signal from the feedback circuit is used to precisely control the MCT conduction regions. The parallel current sharing structure of the variable conduction region MCT has the advantages of high integration, small size, and high stability. Attached Figure Description

[0017] Figure 1 This is an overall structural diagram of a parallel current sharing structure of a variable conduction region MCT in this invention.

[0018] Figure 2 This is a schematic diagram of the CS-MCT structure in this invention.

[0019] Figure 3 This is a schematic diagram of the gate structure of an MCT device with a variable conduction region according to the present invention. Detailed Implementation

[0020] The technical solution of the present invention will now be described in detail with reference to the accompanying drawings:

[0021] This invention provides a parallel current-sharing structure for a variable conduction region MCT, including a gate drive circuit, a pulse discharge circuit, a feedback circuit, and a gate control circuit. The gate drive circuit is powered by an external low-voltage source, and its output is a pulse voltage signal, which provides a gate drive signal to the gate control circuit for gate driving in the conduction region of the MCT. The pulse discharge circuit mainly consists of a resistor, a high-voltage capacitor, and the MCT with a variable conduction region. When the MCT is in the blocking state, it has current blocking capability, and the voltage of the external high-voltage source is fully applied across the high-voltage capacitor, which charges rapidly and stores a large amount of energy. When the MCT is on, the resistance is very small and has excellent surge current capability. The high-voltage capacitor discharges to the resistor through the discharge circuit via a damped oscillation, generating an extremely high pulse current output.

[0022] The feedback circuit samples the pulse discharge current of the discharge circuit through sampling resistors, coils, etc., compares the peak value of the pulse current of the discharge circuit, and provides a feedback signal V to the gate control circuit. Feedback The gate control circuit receives the feedback signal V from the feedback circuit. Feedback Compare VFeedback With preset threshold V Fn This determines whether each zone is turned on or off. The on zone is provided with the same gate drive signal by the gate drive circuit, while the gate voltage of the off zone is 0.

[0023] The aforementioned Variable On-Time (MCT) utilizes a layout partitioning method, dividing the layout into one normally on-time region and multiple variable on-time regions. Dielectric isolation protects the partitions, preventing current from flowing between different regions. Different partitions have independent gate pads and are not interconnected; devices within the same partition have their own independent polygate connections. The normally on-time region is continuously powered by a gate drive circuit, which releases energy from the high-voltage capacitor to establish the initial small pulse.

[0024] The multiple variable conduction regions are each controlled by a different gate control circuit, and each gate control circuit has a different preset voltage signal (V). F1 V F2 ......V Fn ), and simultaneously receive the feedback signal V provided by the feedback circuit. Feedback When V Feedback <V Fn When the corresponding zone is activated, the pulse current increases due to superposition; when V Feedback ≥V Fn When the corresponding zone gate is grounded, the zone remains off, blocking current flow.

[0025] Furthermore, this invention employs an MCT device as a power semiconductor switch. The MCT device combines the simplicity of the MOSFET gate control circuit with the excellent surge current capability of the thyristor. Due to the presence of the cathode short-circuit region, the device can maintain high-voltage blocking characteristics when the gate voltage is 0. At the same time, the presence of the thyristor structure after turn-on enables the device to provide a di / dt greater than 10 kA / μs and a pulse current peak of several thousand amperes.

[0026] Furthermore, this invention employs a gate layout partitioning and threshold hierarchical control method, where the peak current is determined by the number of partitions involved in real time, and the number of partitions increases with V. Feedback Closed-loop regulation can be achieved by adjusting V. Fn The size of the current allows the discharge circuit to output a continuously adjustable peak current. Furthermore, because this method solves the problems of current distribution and thermal breakdown risk at the device level in one go, it eliminates the need for external current-sharing resistors or magnetic components. The parasitic inductance of each branch is less than 5 nH, resulting in advantages such as high integration, small size, and high stability.

[0027] like Figure 1The diagram shows the overall structure of a parallel current-sharing structure for a variable conduction region MCT according to the present invention. The parallel current-sharing structure of the variable conduction region MCT includes four modules: a gate drive circuit, a pulse discharge circuit, a feedback circuit, and a gate control circuit. The gate drive circuit is powered by an external low-voltage source, and its output is a pulse voltage signal, providing a gate drive signal to the gate control circuit for driving the gates of the MCT conduction regions. The pulse discharge circuit consists of a resistor, a high-voltage capacitor, and a variable conduction region MCT. The high-voltage capacitor is powered by a high-voltage power supply and pulses to the resistor to generate a pulse current. The MCT has multiple gate conduction regions 1 to n. During discharge, the pulse discharge current signal changes with the conduction regions, which are controlled by the gate control circuit. The feedback circuit, when the pulse discharge circuit generates an extremely high pulse current output, samples the peak value of the pulse current in the discharge circuit and compares the magnitude of the peak value, providing a feedback signal V to the gate control circuit. Feedback The gate control circuit receives the feedback signal V from the feedback circuit. Feedback This precisely controls the conduction status of the MCT gate region. The conduction region receives the same gate drive signal from the gate drive circuit, while the gate voltage in the non-conducting region is 0. When the pulse current of the discharge circuit is too small, the feedback signal V... Feedback The voltage signal V is less than the threshold preset voltage signal of the gate control circuit. F When the corresponding area is opened, the peak value of the pulse current in the discharge circuit is compensated and increased; when the pulse current in the discharge circuit is too large, the feedback signal V... Feedback The voltage signal V is greater than the threshold preset voltage signal of the gate control circuit. F The corresponding control area is shut down, and the peak pulse current of the discharge circuit decreases.

[0028] like Figure 2 The diagram shows the structure of the CS-MCT in this invention. When the gate voltage exceeds the threshold voltage, a strong inversion occurs on the surface of the P-well, forming an electron channel. The electron current from the cathode is injected into the N-drift region through the electron channel of the P-well. When a forward voltage is applied to the anode and cathode of the MCT, the emitter junction of the PNP transistor is forward biased, and the collector junction is reverse biased, thus turning on and entering the amplification state. During the conduction process of the PNP, the anode outputs a hole current. The holes enter the P-well through the base drift region of the PNP transistor, acting as the base current of the NPN transistor. When α... PNP + α NPNWhen the voltage is ≥ 1, the thyristor turns on, and the MCT device turns on. When the voltage on the gate is less than or equal to 0V, a strong inversion hole channel is formed in the N-well region below the gate. The hole current injected into the P-well is pumped away from the cathode through the hole channel and the P-well, resulting in fast turn-off. The MCT combines the simplicity of the MOSFET gate control circuit with the excellent surge current capability of the thyristor. It can respond quickly when turned on, has low conduction power loss, and can provide high di / dt and high peak current. At the same time, the MCT has a fast turn-off speed, solving the problem of difficult turn-off of traditional thyristors.

[0029] like Figure 3 The diagram shows a gate structure of a variable conduction region MCT device according to the present invention. This structure divides the MCT into seven regions, with each region's edges electrically isolated using an insulating dielectric material to prevent current from flowing across the device's anode and cathode. Within each region, strip-shaped polysilicon gates are deposited on all N-wells and P-wells. These polysilicon gates are interconnected within the same region, while polysilicon gates in different regions are separated by an insulating dielectric material. In regions where the polysilicon gate voltage exceeds the threshold voltage, strong inversion occurs on the P-well surface, forming an electron channel. The anode and cathode at both ends of the partition are conductive, allowing pulse current to flow. Conversely, when the gate voltage is below the threshold, the region maintains high impedance, and current is blocked. Figure 3 As shown, region (1) is the normally conducting region, and regions (2) to (7) are variable conducting regions. The normally conducting region is always powered by the driving circuit and is used to release energy from the high-voltage capacitor in the pulse discharge circuit to establish a reference pulse current. The gate voltage of the multiple variable conducting regions is generated by an independent control circuit and compared with the real-time current peak value of the discharge circuit. When the detected current increases to the corresponding partition threshold, the corresponding gate voltage is raised, so that the partition is turned on, and the total current is compensated in stages. When the current falls back, the gate voltage is pulled down, and the partition is turned off again. Through the staged and closed-loop adjustment of the gate voltage, the system can achieve accurate compensation and uniform distribution of pulse discharge current without additional current sharing components.

Claims

1. A variable conduction region MCT parallel current sharing circuit, characterized in that, It includes a gate drive circuit, a pulse discharge circuit, a feedback circuit, and a gate control circuit; The gate drive circuit is powered by an external low-voltage power supply and outputs a pulsed gate voltage signal to the gate control circuit. The pulse discharge circuit includes a high-voltage capacitor, a resistor, and a variable conduction section (MCT). The pulse discharge circuit is powered by an external high-voltage power supply, which charges the high-voltage capacitor. The high-voltage capacitor, resistor, and MCT are connected to form a discharge circuit. When the MCT is in the blocking state, the voltage of the external high-voltage source is fully applied across the high-voltage capacitor. When the MCT is in the opening state, the high-voltage capacitor discharges to the resistor through the discharge circuit via a damped oscillation method, generating a high-pulse current output. The feedback circuit samples the pulse discharge current of the discharge circuit, compares the peak value of the pulse current of the discharge circuit, and provides a feedback signal for the gate control circuit. The gate control circuit controls the conduction region of the variable conduction region MCT under the combined action of the pulse gate voltage signal and the feedback signal, and determines whether each zone is turned on or off. The variable conduction region (MCT) is implemented by dividing the MCT into multiple regions, one of which is a fixed normally-on region, while the others are variable conduction regions. Specifically, the MCT is isolated into multiple regions by an insulating dielectric material. Strip-shaped polysilicon gates are deposited on the N-wells and P-wells within each region. The polysilicon gates within the same region are interconnected, while the polysilicon gates in different regions are separated by the insulating dielectric material. In regions where the polysilicon gate voltage is higher than the threshold voltage, strong inversion occurs on the P-well surface to form an electron channel, and the anode and cathode at both ends of the partition are conductive, allowing pulse current to flow. Conversely, when the gate voltage is lower than the threshold, the corresponding region maintains high impedance, and the current is blocked. The normally-on region is always powered by the driving circuit and is used to release energy from the high-voltage capacitor in the pulse discharge circuit to establish a reference pulse current. The gate voltage for the remaining variable conduction region is generated independently by the gate control circuit.

2. The variable conduction region MCT parallel current sharing circuit according to claim 1, characterized in that, The method by which the gate control circuit controls the variable conduction region of the variable conduction region MCT is to preset a threshold voltage signal V for each variable conduction region of the variable conduction region MCT in the gate control circuit. Fn , where n is the variable conduction region number, n=1, 2, …; the feedback signal is defined as V. Feedback When V Feedback < V Fn When V is active, the corresponding variable conduction region and normally active region are turned on synchronously, and the conduction region is provided with the same gate drive signal by the gate drive circuit; when V Feedback ≥ V Fn When the variable conduction region is turned on, the gate is grounded and the gate voltage is forced to zero. When the variable conduction region is turned on, the peak value of the pulse current in the discharge circuit is compensated and increased. When the variable conduction region is turned off, the peak value of the pulse current in the discharge circuit decreases.

3. The variable conduction region MCT parallel current sharing circuit according to claim 2, characterized in that, The variable conduction region MCT is a MOS-controlled thyristor with a cathode short-circuit structure. When the cathode is short-circuited to ensure that the gate voltage is zero, the device maintains high voltage blocking. After being turned on, it relies on the thyristor structure to provide high di / dt and high pulse current peak.

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