Controller for switching regulator, switching regulator and light source

1. A controller for a switching regulator, comprising:

a hysteretic comparator ( 12 , 30 ) for controlling a switch ( 15 ) for switching current into an inductor ( 3 ),

a first circuit ( 6 , 9 ) including a first voltage to current converter ( 6 ) for supplying a first signal representing instantaneous current in the inductor ( 3 ), when the switch is in an on state and when the switch is in an off state, to the comparator ( 12 , 30 ),

a second circuit ( 36 , 37 , 41 , 42 ) including a second voltage to current converter ( 36 ) for supplying a second signal to the comparator, the second signal representing an error between a desired regulator output and a representation of an actual regulator output, and

the comparator having a first input terminal arranged to receive the first signal and the second signal.

2. The controller according to claim 1 wherein the second signal is an averaged signal applied as a negative feedback signal modifying the first signal to the comparator ( 12 , 30 ) whereby an averaged inductor current is controlled.

3. The controller as claimed in claim 1 , characterized in that the second circuit ( 36 , 37 , 41 , 42 ) has a slower response time than the first circuit ( 6 ).

4. The controller as claimed in claim 1 , characterized in that the second circuit ( 36 , 37 , 41 , 42 ) includes an integrator ( 42 ).

5. A controller as claimed in claim 4 , characterized in that the integrator ( 42 ) is arranged to integrate the difference between the desired regulator output and the representation of the actual regulator output.

6. A controller as, claimed in claim 4 , characterized in that the integrator ( 42 ) has a time constant of the order of several switching cycle periods during operation of the regulator.

7. A switching regulator characterized by comprising a controller as claimed in claim 1 and the inductor ( 3 ).

8. The regulator as claimed in claim 7 characterized by comprising a first sensing resistor ( 5 ) in series with the inductor ( 3 ) and connected to the first circuit ( 6 ).

9. The regulator as claimed in 8 characterized in that the first sensing resistor ( 5 ) is connected to the second circuit ( 36 , 37 , 41 , 42 ).

10. The regulator as claimed in claim 8 , characterized by comprising a second sensing resistor ( 56 ) in series with an output ( 1 ) of the regulator and connected to the second circuit ( 36 , 37 , 41 , 42 ).

11. The regulator as claimed in claim 7 characterized in that an, or the, output ( 1 ) of the regulator is connected to the inductor ( 3 ) via a diode ( 4 ).

12. A light source characterized by comprising at least one light emitting device ( 1 ) connected to a regulator as claimed in claim 7 .

13. A controller for a switching regulator, comprising:

a hysteretic comparator ( 12 , 30 ) for controlling a switch ( 15 ) for switching current into an inductor ( 3 ), the comparator ( 12 , 30 ) having upper and lower thresholds;

a first circuit ( 6 , 9 ) for supplying a first signal, representing instantaneous current in the inductor ( 3 ), to the comparator ( 12 , 30 ); and

a second circuit ( 36 , 37 , 41 , 42 ) for supplying a second signal to the comparator, representing an, error between a desired regulator output and an actual regulator output,

characterized in that the first and second circuits ( 6 , 36 , 37 , 41 , 42 ) have first and second inputs, respectively, which are connectable or connected together and the second circuit ( 36 , 37 , 41 , 42 ) includes a gate ( 57 ) arranged to pass a signal from the second input when the switch ( 15 ) is off and to block the signal from the second input when the switch ( 15 ) is on.

14. The controller as claimed in claim 13 , characterized in that the gate ( 57 ) is arranged to be controlled by the comparator ( 12 , 30 ).