Linear post-regulator
The invention describes a linear post-regulator ( 1 ) realized for use in an LED lighting arrangement ( 2 ), which linear post-regulator ( 1 ) comprises a control loop cascade (L 1 , L 2 , L 3 ) realized for connection between a terminal of an LED lighting load ( 20 ) and a power converter ( 21 ) of the LED lighting arrangement ( 2 ); a transistor (Q) realized to regulate an LED current (I LED ) through the LED lighting load ( 20 ); a first input ( 11 ) for connection to a reference current input (I ref ); a second input ( 12 ) for connection to a performance parameter input (V ref , Δlref); and an output for connecting a power control output (Pctr) of the linear post-regulator ( 1 ) to the power converter ( 21 ); wherein the control loop cascade (L 1 , L 2 , L 3 ) comprises at least two interconnected control loops (L 1 , L 2 , L 3 ) to regulate the LED current (I LED ) on the basis of the reference current input (Iref) and to regulate a further performance parameter of the LED lighting arrangement ( 2 ) on the basis of the performance parameter input (V ref , Δlref). The invention also describes an LED lighting arrangement ( 2 ), and a method of post-regulating the current of an LED lighting load ( 20 ) of an LED lighting arrangement ( 2 ).
1. A linear post-regulator realized for use in an LED lighting arrangement, which linear post-regulator comprises
a control loop cascade realized for connection between a terminal of an LED lighting load and a power converter of the LED lighting arrangement;
a transistor (Q) realized to regulate an LED current (I LED ) through the LED lighting load;
a first input ( 11 ) for connection to a reference current (I ref );
a second input for connection to a reference current ripple (V ref , ΔIref); and
an output for connecting a power control output (Pctr) of the linear post-regulator to the power converter;
wherein the control loop cascade comprises at least two interconnected control loops to regulate the LED current (I LED ) on the basis of the reference current input (I ref ) and to adjust current ripple of the LED lighting arrangement on the basis of the reference current ripple (V ref , ΔI ref ).
2. A linear post-regulator according to claim 1 , wherein the reference current ripple input (V ref , ΔIref) comprises a reference voltage (V ref ), and wherein the control loop cascade is realized to adjust an output voltage (V bus ) of the power converter on the basis of the reference voltage (V ref ).
3. A linear post-regulator according to claim 1 , comprising a first control loop realized to provide a control signal (Q control ) to the transistor (Q).
4. A linear post-regulator according to claim 3 , wherein the control signal (Q control ) is generated on the basis of the first loop reference current (I ref _ L1 ) provided by the second control loop.
5. A linear post-regulator according to claim 1 , comprising a second control loop realized to generate a first loop reference current (I ref _ L1 ) on the basis of the reference current input (I ref ) and a current through the transistor (Q).
6. A linear post-regulator according to claim 1 , comprising a third control loop realized to provide a power control output (P ctr ) to the converter on the basis of the reference current ripple input (V ref , ΔIref) and a voltage (V PR ) across the post-regulator.
7. A linear post-regulator according to claim 1 , wherein the transistor (Q) comprises a MOSFET, preferably an n-channel depletion-mode MOSFET.
8. A linear post-regulator according to claim 1 , wherein a control loop comprises a number of operational amplifiers.
9. An LED lighting arrangement comprising
a single-stage power converter for connection to a power supply;
an LED lighting load comprising a number of LEDs;
a linear post-regulator according to claim 1 connected between a terminal of the LED lighting load and a terminal of the power converter; and
an input means for providing a reference current input (I ref ) and a reference current ripple input (V ref , ΔIref) to the linear post-regulator.
10. An LED lighting arrangement according to claim 9 , wherein the power converter comprises a switched-mode power converter with power factor correction.
11. An LED lighting arrangement according to claim 10 , wherein an input means is connected to a local signal source within the LED lighting arrangement and/or an input means is connected to a remote signal source.
12. A method of post-regulating the current of an LED lighting load of an LED lighting arrangement, which method comprises the steps of
providing a post-regulator ( 1 ) comprising a control loop cascade of at least two interconnected control loops for connection between a terminal of the LED lighting load and a power converter of the LED lighting arrangement, and a transistor (Q) to regulate an LED current (I LED ) through the LED lighting load;
providing to the post-regulator a first input for connection to a reference current input (I ref ); and
providing to the post-regulator a second input for connection to a reference current ripple input (V ref , ΔIref);
applying the control loop cascade to regulate the LED current (I LED ) on the basis of the reference current input (I ref ) and to adjust current ripple of the LED lighting arrangement on the basis of the reference current ripple input (V ref , ΔIref).
13. A method according to claim 12 , wherein regulation losses of the post-regulator are controlled on the basis of the power control output (P ctr ) from a control loop of the control loop cascade when the reference current ripple input (V ref ) comprises a reference voltage input (V ref ).