A control circuit of an oxygen concentrator maintains pressure within a compressor of the oxygen concentrator. The control circuit includes a microprocessor that controls functioning of a controller based on two or more of: a user-adjustable flow rate of oxygen delivered by the oxygen concentrator to a user, an ambient temperature, and an ambient pressure. The functioning of the controller further controls the adsorption of various gases by sieve beds of the oxygen concentrator to produce oxygen enriched gas.