Reivindicaciones
1. Control system for train doors comprising power control means of the motor (5) operating the doors in charge of regulating the voltage, reversing the polarity or rotation of and applying a brake to said motor (5), state and position control means of said doors and a microprocessor (7) which processes the external controlling open and close signals, as well as those of said state and position control means of said doors to perform, from this information, the control of the motor through the power control means of said motor, characterized in that the power control means of the motor (5) comprise a single bridge of four transistors (1, 2, 3 and 4), and in that the state and position control means of the doors comprise: - an encoder coupled to the shaft of the motor (5) for determining the position, speed and direction of the door; - a limit switch for detecting the complete closing of the door and its mechanical anchoring; and - means for determining the overcurrent occurring in the motor (5) due to the blocking of the shaft occurring when the door reaches the end of its travel, performing a triple-check of the state and position of said doors. 2. Control system for train doors according to claim 1, characterized in that the bridge of four transistors (1, 2, 3 and 4) adopts a full bridge configuration. 3. Control system for train doors according to claim 2, characterized in that the transistors (1, 2, 3 and 4) are MOSFET type transistors. 4. Control system for train doors according to claim 1, characterized in that the encoder coupled to the shaft of the motor (5) for determining the position, speed and direction of the door is a high-resolution encoder (8). 5. Control system for train doors according to claim 1, characterized in that the limit switch for detecting the complete closing of the door and its mechanical anchoring is a contact-free magnetic sensor (9). 6. Control system for train doors according to claim 1, characterized in that the means for determining the overcurrent measured in the motor (5) comprise an analog-to-digital converter (10) which samples the voltage applied to said motor (5) and a sensor for sampling the current circulating therethrough. 7. Control system for train doors according to claim 6, characterized in that the sensor for sampling the current circulating through the motor (5) is a Hall effect sensor (11). 8. Control system for train doors according to claim 1, characterized in that in order to respond to malfunction situations of the microprocessor (7), it comprises a hardware device (13) operated by the close line preventing the bridge of transistors (1, 2, 3, 4) from being able to command the motor (5) to open the doors if there is a close order, preventing said doors from opening accidentally. 9. Control system for train doors according to claim 9, characterized in that the hardware device (13) has means capable of blocking the transistor (1) of the upper branch of the bridge of transistors (1, 2, 3, 4), shunting its door to ground and preventing it from being able to command the motor in open mode. 10. Control system for train doors according to claim 1, characterized in that it comprises a stage (12) in the voltage supply prior to the power stage which allows the microprocessor (7) to inhibit the supply in unsafe situations. 11. Control system for train doors according to claim 10, characterized in that analyzer software is implemented in the microprocessor (7) for checking the proper working of the system. 12. Method for operating train doors based on the system of claims 1 to 11, characterized in that the operation of the four transistors (1, 2, 3, 4) making up the power control means of the motor (5) for regulating the voltage, reversing the polarity or rotation of and applying a brake to said motor (5) comprises the stages of: - activating the rotation of the motor (5) in one direction; - activating the rotation of the motor (5) in the other direction; - applying a brake to the motor (5); and - releasing the brake, wherein the stage of applying a brake to the motor (5), in addition to being applied in situations in which doors are to offer great resistance to manual displacement, is additionally applied for a short time period in the transition between the other three stages of rotation in one direction, rotation in the other direction and the brake release situation such that the current of the motor (5) recirculates, being canceled. 13. Method for operating train doors according to claim 12, characterized in that to activate the rotation of the motor (5) in one direction or in the other direction, two transistors located in the same side branch are tripped in push-pull whereas one of the transistors in the other branch is tripped and the other one is kept off. 14. Method for operating train doors according to claim 13, characterized in that in order to prevent high voltage pulses during the tripping in push-pull of the transistors located in the same side branch, the driving time of the transistor located at the lower part (3, 4) in said side branch is acted on to control the amount of energy that will be returned to the supply and that which will be recirculated until the following cycle. 15. Method for operating train doors according to claims 13 and 14, characterized in that the trip in push-pull of the transistors located in the same side branch is a function of the voltage that is to be applied to the motor (5) and therefore of the desired rotation speed thereof, which determines the speed and pressure of the doors. 16. Method for operating train doors according to claim 12, characterized in that the stage of applying a brake to the motor comprises the operation of keeping transistors (1) and (2) of the upper branches on and transistors (3) and (4) of the lower branches off, or vice versa. 17. Method for operating train doors according to claim 12, characterized in that the stage of releasing the brake in the motor (5) comprises the opening of four transistors (1, 2, 3, 4), the current generated by the motor (5) being driven again by the intrinsic diodes (6) of the transistors towards the supply such that the door can be manually displaced. 18. Method for operating train doors according to claim 12, characterized in that prior to the stages of activating in one direction or in the other, applying a brake and releasing the brake in the motor (5), the door is located by applying voltage to said motor (5) so that the latter displaces it at a low speed in the appropriate open or close direction, until it reaches the end of travel, taking said position as a reference.
