Mitsubishi QM20TD-H 600V 20A Darlington Module: Technical Overview and Specifications
QM20TD-H Mitsubishi 600V 20A Darlington Module
The Mitsubishi QM20TD-H is a 6-in-1 isolated three-phase Darlington transistor module designed for medium-power switching applications in power semiconductors. By integrating six Darlington pairs into a single package, the module provides a compact layout that minimizes parasitic inductance.
- Core Specifications: 600V VCEX(sus) | 20A IC | 3-Phase Bridge Configuration
- Key Advantages: Symmetrical internal routing reduces loop area to mitigate EMI, and the housing simplifies overall electrical layout.
- Thermal Management: Features an isolated baseplate to ease thermal coupling to a single heatsink.
Download Official Datasheet (PDF)
Technical Analysis of the 6-in-1 Topology
The QM20TD-H is engineered around a 6-in-1 topology, placing three half-bridge branches into a unified housing. This integration is crucial for reducing stray inductance. In high-speed switching circuits, stray inductance acts like a microscopic spring that stores energy and releases it as voltage spikes during turn-off. By consolidating the wiring within the module, the loop inductance is minimized, protecting the internal silicon from transient overvoltages.
A key parameter of the module is the sustaining collector-emitter voltage, VCEX(sus), rated at 600V. This voltage dictates the maximum safe DC bus voltage the module can block when the transistors are in an off-state. Working in tandem with this is the DC current gain (hFE), which typically reaches a minimum of 75 at a collector current of 20A. High current gain reduces the drive current required from the base control circuitry. This allows engineers to use smaller, lower-power drive optocouplers and discrete base-drive components.
Thermal management is guided by the junction-to-case thermal resistance (Rth(j-c)). You can think of thermal resistance as the narrowness of a physical water pipe. A lower thermal resistance represents a wider pipe, allowing heat to flow easily away from the silicon junctions to the heatsink. The QM20TD-H utilizes a ceramic-insulated baseplate to achieve a low thermal resistance of 1.25°C/W while maintaining an electrical isolation voltage rating of 2500V AC. This allows multiple modules to be mounted on a single heatsink without external insulating sheets.
Optimized Industrial Applications
- AC Motor Drives: The 3-phase configuration matches the requirements of variable frequency drives operating on 220V AC input lines.
- Servo Control Systems: The 20A current rating and high gain make the module suitable for controlling fractional horsepower AC/DC servo motors.
- Uninterruptible Power Supplies (UPS): The 600V blocking voltage allows for reliable power inversion in backup power topologies.
- Legacy Industrial Controls: An ideal replacement for maintenance and repair of older industrial machinery using legacy Darlington transistor modules.
Best Match: The QM20TD-H is best suited for legacy 220V AC motor drives requiring a compact, integrated 3-phase switching stage with low drive current requirements.
Key Technical Specifications
| Parameter | Symbol | Rating / Value |
|---|---|---|
| Collector-Emitter Sustaining Voltage | VCEX(sus) | 600 V |
| Collector Current (DC) | IC | 20 A |
| Collector Dissipation (Per Transistor) | PC | 100 W |
| DC Current Gain (IC = 20A, VCE = 2V) | hFE | 75 (Min) |
| Isolation Voltage (RMS, 1 minute) | Viso | 2500 V AC |
| Junction-to-Case Thermal Resistance | Rth(j-c) | 1.25 °C/W (Max) |
Engineer FAQ
Q1: What are the base drive requirements for the QM20TD-H?
A1: Due to the Darlington configuration, base drive current requirements are low. At a collector current of 20A, the base current needed to saturate the transistor is 0.4A, allowing control via low-power driver circuits.
Q2: How should the thermal dissipation of the QM20TD-H be calculated?
A2: Use the maximum thermal resistance of 1.25°C/W per transistor. Under operating conditions, the maximum junction temperature must not exceed 150°C. Calculate the heatsink size based on this resistance and the thermal interface material used.
Q3: Does the module contain integrated free-wheeling diodes?
A3: Yes. The QM20TD-H features integrated fast-recovery free-wheeling diodes connected anti-parallel to each transistor. These diodes clamp inductive voltage spikes, eliminating the need for external discrete clamping components.
Closing Technical Summary
The QM20TD-H provides a compact, integrated option for three-phase power switching applications. By combining low thermal resistance and high DC gain into a single isolated module, it remains a reliable platform for medium-power conversion systems and maintenance legacy designs.