design for amateurs 40A stabilized power supply circuit

This power supply is designed for amateur use and has been operational for over 10 years. Its design is straightforward and largely resistant to radio frequency interference (RF). The system incorporates various components, with the most significant being a 600VA toroidal transformer, which can be substituted with another transformer of different specifications if necessary, within a voltage range of 17V to 20V. A reference voltage of 7.5V is established using a Zener diode (6.8V to 8.2V), which is applied to Q2. This transistor compares the input voltage from a resistive voltage divider composed of R5, R6, and VR2, and controls a Darlington amplifier (Q3) responsible for driving the output stage. The output stage includes a driver transistor (Q4) and four 2N3771 NPN power transistors, which can be mounted directly onto a heat sink without insulation, as their collectors are grounded. The power supply features a current limit circuit (Q1), adjustable via VR1, along with an overload LED indicator (DL2) and comprehensive short circuit protection. In the event of a short circuit, the power supply can maintain zero consumption indefinitely without risk. It is important to note that due to the high power capability of this supply, even a brief short circuit through a cable of adequate gauge should not exceed the maximum current of 40A. An active rectifier configuration (D1, D2) is recommended, with the cathode connected to the ground and a sufficiently large heat sink installed. The power transistors should be mounted on a heatsink as high as possible without insulation, which may be integrated into an aluminum frame. Mechanical ventilation with a thermostat is also advised.

The power supply circuit is designed to provide stable and reliable operation for various amateur applications. The inclusion of a 600VA toroidal transformer serves as the primary power source, which is favored for its low electromagnetic interference and efficient performance. The Zener diode establishes a stable reference voltage, which is crucial for maintaining consistent output under varying load conditions.

The resistive voltage divider composed of R5, R6, and VR2 allows for precise voltage regulation, enabling the system to adapt to different input voltages while ensuring that the output remains within the desired range. The Darlington amplifier configuration (Q3) enhances the current gain, ensuring that even small input signals can effectively drive the output stage.

The use of four 2N3771 NPN transistors in the output stage allows for significant power handling capabilities, making this power supply suitable for high-current applications. The direct mounting onto a heat sink without insulation simplifies the thermal management process, as grounding the collectors minimizes the risk of electrical isolation failures.

The current limiting feature (Q1) is an essential safety mechanism, adjustable via VR1, that protects the power supply from excessive current draw, which could lead to overheating or component failure. The overload LED (DL2) provides a visual indication of potential issues, allowing for immediate corrective action.

Short circuit protection is a critical aspect of the design, enabling the power supply to enter a low-power state during a fault condition, thereby preventing damage to both the power supply and connected devices. The recommendation to use an adequately gauged cable is important to ensure that the system can handle high currents without risking damage due to overheating or electrical arcing.

The active rectifier configuration (D1, D2) enhances the efficiency of the power conversion process, ensuring that power loss is minimized during operation. The implementation of a substantial heat sink and mechanical ventilation is vital for maintaining optimal operating temperatures, especially under heavy load conditions, thus prolonging the lifespan and reliability of the power supply.This power supply is designed for amateurs, and has been in operation for over 10 years. Its design is very simple and practically immune to RF. It brings together the individual pieces, is the most expensive part of 600VA toroidal transformer, which can be replaced by another with different characteristics, in the case of a voltage between 17 ~ 2 0V power and right for our needs. Reference voltage of 7. 5 V Zenner diode (6V8 ~ 8V2), shall apply to Q2, which compares the input resistive voltage divider consisting of R5, R6 and VR2, steering Darlington amplifier Q3, which is responsible for driving the output stage, which consists of a driver in Q4 and 4 2N3771 NPN power transistor, which can be mounted directly on the heat sink without insulation, since it is a collector grounded. The source has a current limit (Q1), adjusted by VR1 and overload LED (DL2) and full protection against short circuits, with zero consumption in case of short circuit can be maintained indefinitely in this state without danger.

(Please note that due to the strong power of the power supply with a casual a short length of cable, high or small section that is strong enough to not exceed the maximum current of 40A. Can not be considered a short circuit and cause the supply of a power supply large amounts of energy).

active rectifier (D1, D2) is recommended for a type of cathode metal screw is on the ground, install a heat sink large enough block. As power transistors using a hedgehog as high as possible, without being isolated as above, can be part of the window of an aluminum frame.

We also recommend using mechanical ventilation with the thermostat. 🔗 External reference