Circuit Arrangement and Method of Driving a Circuit Arrangement

• US 20080265981A1
• Filed: 11/01/2006
• Published: 10/30/2008
• Est. Priority Date: 11/08/2005
• Status: Active Grant

• Current Assignee: Philips Lighting Holding BV (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Clout, Ramon Antoine Wiro, Niessen, Patrick Catharina Johannes Gerardus
• Granted Patent: US 7,834,678 B2
• Time in Patent Office: Days
• US Class Current: 327/436
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/24 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices

Abstract

The present invention relates to controlling switches in a series connection of electrical devices, in particular to a circuit arrangement, and method of operating same, in which a transistor switch (44, 54) is used to control operation of the devices (12, 14). Because the transistor switches need a gate-source voltage difference, but on the other hand are connected with their source (s) and drain (d) to the main circuit branch, this voltage difference is built up by providing a control current (Ii, I2) over e.g. a resistor (42, 52). This control current (Ii, I2) enters the main current (I), which would influence the operation of the devices, e.g. LEDs (12, 14). In order to correct this, the control current (I2) is corrected for the values of one or more upstream control currents (I2), e.g. through adapting the pulse width in pulse width modulation.

Claims

1. A circuit assembly (1), comprising

a connection for an electrical power source (10) for supplying an electrical current to the circuit assembly,

at least one first electrical device (12, 14) and at least one second electrical device (14, 16), connected in series therewith,

at least one semiconductor switch (22, 24) for controlling said first electrical device (12, 14), and comprising at least a gate (g), a source (s) and a drain (d), and connected in parallel with said first electrical device (12, 14) by means of the drain (d) and the source (s),

a control unit (30) arranged for supplying a first control signal to the semiconductor switch (22, 24) and a second control signal to said second electrical device (14, 16),

wherein said second electrical device (14, 16) is present downstream of said first electrical device (12, 14) and said semiconductor switch (22, 24), in the direction of a current flow when the circuit arrangement is in use,

wherein at least one electrical component (40, 42, 50, 52) is provided between the gate (g) and the source (d), across which electrical component a voltage difference develops when a current (I₁, I₂) is sent through the component, wherein furthermore the first control signal comprises a control current signal to the gate (g) and to the electrical component (40, 42, 50, 52),

wherein the control unit (30) is arranged to adapt the second control signal in dependence on the first control signal.

2. The circuit arrangement of claim 1, wherein the semiconductor switch (22, 24, 26) comprises an insulated gate transistor switch.

3. The circuit arrangement of claim 2, wherein the insulated gate transistor (22, 24, 26;

44, 54) switch comprises a JFET or a MOSFET.

4. The circuit arrangement of claim 1, wherein the electrical component comprises a resistor (42, 44).

5. The circuit arrangement of claim 4, wherein the resistance has a value of between 0.5 and 500 kΩ

, preferably between 1 and 100 kΩ

.

6. The circuit arrangement of claim 1, wherein the second electrical device (14, 16) comprises an additional insulated gate semiconductor switch (54), for controlling said second electrical device (14) and comprising at least a gate (g), a source (s) and a drain (d), and connected in parallel with said second electrical (14) device by means of the drain (d) and the source (s).

7. The circuit arrangement of claim 1, wherein the first and/or second electrical device comprises a LED (12, 14).

8. The circuit arrangement of claim 1, wherein the first and/or second control signal comprises a pulse width modulated current signal having a duty cycle.

9. The circuit arrangement of claim 8, wherein the duty cycle of the second control signal is dependent on the first control signal.

10. The circuit arrangement of claim 1, comprising a plurality of first and second electrical devices (12, 14, 16) that are connected in series, and a plurality of semiconductor switches (22, 24, 26) that are each connected in parallel with one or more of the plurality of first and second electrical devices (12, 14, 16),

wherein the control unit (30) is arranged to provide each of the semiconductor switches with a respective control signal, and

wherein the control unit (30) is furthermore arranged to adapt the respective control signal of each particular semiconductor switch (24, 26) in dependence on all of the respective control signals for all of the semiconductor switches (22, 24) upstream said particular semiconductor switch (24, 26).

11. The circuit arrangement of claim 1, wherein the circuit arrangement comprises a first, second and third electrical device (12, 14, 16), connected in series, and each having connected in parallel thereto a respective semiconductor switch (22, 24, 26) that is able to receive a respective control signal from a control unit (30), wherein the control signal for a particular semiconductor switch (24, 26) is dependent on the respective control signals for all semiconductor switches (22, 24) upstream of said particular semiconductor switch (24, 26).

12. Method of driving a circuit arrangement (1) with at least one first electrical device (12) and at least one second electrical device (14, 16) connected in series therewith, by means of a semiconductor switch (22;

44) for controlling said first electrical device (12), the semiconductor switch comprising at least a gate (g), a source (s) and a drain (d), and connected in parallel with said first electrical device (12) by means of the drain and the source, wherein said second electrical device (14, 16) is present downstream of said first electrical device (12) and said semiconductor switch (22;

44), in the direction of a current flow when the circuit arrangement is in use, the method comprising

providing a first control signal between the gate (g) and the source (s), that switches the semiconductor switch (22;

44), in order to control the first electrical device (12);

providing a second control signal to control the second electrical device (14, 16),

wherein the second control signal is determined in dependence on the first control signal.

13. The method of claim 12, wherein the circuit arrangement comprises

a connection for an electrical power source (10) for supplying an electrical current to the circuit assembly,

at least one first electrical device (12, 14) and at least one second electrical device (14, 16), connected in series therewith,

at least one semiconductor switch (22, 24) for controlling said first electrical device (12, 14), and comprising at least a gate (g), a source (s) and a drain (d), and connected in parallel with said first electrical device (12, 14) by, means of the drain (d) and the source (s),

a control unit (30) arranged for supplying a first control signal to the semiconductor switch (22, 24) and a second control signal to said second electrical device (14, 16),

wherein said second electrical device (14, 16) is present downstream of said first electrical device (12, 14) and said semiconductor switch (22, 24), in the direction of a current flow when the circuit arrangement is in use,

wherein at least one electrical component (40, 42, 50, 52) is provided between the gate (g) and the source (d), across which electrical component a voltage difference develops when a current (I₁, I₂) is sent through the component, wherein furthermore the first control signal comprises a control current signal to the gate (g) and to the electrical component (40, 42, 50, 52),

wherein the control unit (30) is arranged to adapt the second control signal in on the first control signal.

14. The method of claim 12, wherein providing the first control signal (I₁) comprises providing a resistive element (42, 52) between the gate (g) and the source (s) and providing a current signal through the resistive element (42, 52),

and wherein the second control signal (I₂) is determined in dependence on the value of the current signal (I₁).

15. The method of claim 12, wherein a plurality of first and second electrical devices is provided that are connected in series, as well as a plurality of semiconductor switches, that are each connected in parallel with one or more of the plurality of first and second electrical devices, and that each receive a respective control signal,

wherein the respective control signal (I₂) of each particular semiconductor switch (14, 16) is determined in dependence on all of the respective control signals (I₁) for all of the semiconductor switches (12) upstream of said particular semiconductor switch (14, 16).