A negative pressure wound therapy apparatus (20) comprising: a wound dressing (24)； a fluid collection container (38)； a vacuum pump (30) comprising a pump motor (340)； one or more tubes (36) configured to at least channel a fluid flow between said wound dressing (24), said fluid collection container (38), and said pump (30)； a pressure sensor (302) configured to measure a pressure in one or more of said one or more tubes (36) and to generate a pressure output signal； a first control circuit (300) for controlling the pump motor (340) without using a processor, the first control circuit (300) being configured to: generate a difference signal (316) comprising a difference between a contribution of desired pressure and a pressure sensor signal； and generating a motor control signal (318) in response to the difference signal (316)； the motor control signal (318) being configured to control a pump motor speed (340), characterized in that a second control circuit (320) to provide, without using a processor, an override signal (325) based at least in part in the difference signal (316) and at least one reference signal (322), the override signal (325) being configured to override the motor control signal (318) and thereby prevent the The pump motor (340) is heated, wherein the second control circuit (320) comprises a comparison circuit (324) in communication with an AND gate.Un aparato (20) de terapia de heridas por presión negativa que comprende: un vendaje (24) de herida； un recipiente (38) de recogida de fluido； una bomba de vacío (30) que comprende un motor de bomba (340)； uno o más tubos (36) configurados para por lo menos canalizar un flujo de fluido entre dicho vendaje (24) de herida, dicho recipiente (38) de recogida de fluido, y dicha bomba (30)； un sensor (302) de presión configurado para medir una presión en uno o más de dicho uno o más tubos (36) y para generar una señal de salida de presión； un primer circuito (300) de control para controlar el motor (340), de
