A valve unit for controlling the feed of a combustible gas to a burner apparatus, comprising: ∘ a device for regulating the pressure of the gas at the outlet of the unit, including a valve seat associated with a plug, and an operating means for causing the plug to move relatively to the corresponding valve seat, to regulate the outlet feed pressure (Pu) by modulation, wherein the operating means is of the type comprising at least one electromagnet of the proportional type; ∘ a control circuit of the pressure regulating device including a PWM signal generator generating a PWM voltage signal adapted to generate a current signal in the electromagnet in order to move the plug as a function of the magnitude of the current signal and thus determine the outlet pressure (Pu), the magnitude of the current being a function of the duty cycle of the PWM signal; the PWM signal having a frequency such that the operating means is subjected to a mechanical dither having a specified amplitude at least for a specified time interval (T1, T2); ∘ characterized in that the PWM signal generator includes means of controlling the duty cycle and means of controlling the frequency of the PWM signal, the duty cycle control means varying the duty cycle of the PWM signal with the variation of the desired outlet pressure (Pu), and the frequency control means being adapted to vary the frequency of the PWM signal as a function of the variation of the duty cycle so as to keep the amplitude of the dither substantially constant, independently from the variations of the duty cycle of the PWM signal; ∘ and in that the control circuit includes a timer which can access the value of a first and/or a second time interval (T1; T2) stored in the circuit, this timer being active in the first and/or second time interval before and/or after a request to change the outlet gas feed pressure, the frequency variation means being adapted to set the frequency of the first and/or second PWM signal within a range of frequencies capable of generating the dither only when the timer is active, and being adapted to set the frequency of the PWM signal above a frequency level at which the current signal in the electromagnet is substantially constant when the timer is inactive. ∘ a device for regulating the pressure of the gas at the outlet of the unit, including a valve seat associated with a plug, and an operating means for causing the plug to move relatively to the corresponding valve seat, to regulate the outlet feed pressure (Pu) by modulation, wherein the operating means is of the type comprising at least one electromagnet of the proportional type; ∘ a control circuit of the pressure regulating device including a PWM signal generator generating a PWM voltage signal adapted to generate a current signal in the electromagnet in order to move the plug as a function of the magnitude of the current signal and thus determine the outlet pressure (Pu), the magnitude of the current being a function of the duty cycle of the PWM signal; the PWM signal having a frequency such that the operating means is subjected to a mechanical dither having a specified amplitude at least for a specified time interval (T1, T2); ∘ characterized in that the PWM signal generator includes means of controlling the duty cycle and means of controlling the frequency of the PWM signal, the duty cycle control means varying the duty cycle of the PWM signal with the variation of the desired outlet pressure (Pu), and the frequency control means being adapted to vary the frequency of the PWM signal as a function of the variation of the duty cycle so as to keep the amplitude of the dither substantially constant, independently from the variations of the duty cycle of the PWM signal; ∘ and in that the control circuit includes a timer which can access the value of a first and/or a second time interval (T1; T2) stored in the circuit, this timer being active in the first and/or second time interval before and/or after a request to change the outlet gas feed pressure, the frequency variation means being adapted to set the frequency of the first and/or second PWM signal within a range of frequencies capable of generating the dither only when the timer is active, and being adapted to set the frequency of the PWM signal above a frequency level at which the current signal in the electromagnet is substantially constant when the timer is inactive.