Variable bleeder circuit

Patent metadata

Field	Value
Publication number	US-9769901-B1
Application number	US-201615182471-A
Country	US
Kind code	B1
Filing date	Jun 14, 2016
Priority date	Jun 14, 2016
Publication date	Sep 19, 2017
Grant date	Sep 19, 2017

Abstract

A bleeder circuit includes an input current sense circuit, coupled to one of first and second input terminals of a driver circuit, to output a bleeder on/off signal in response to an input current through the first and second input terminals of the driver circuit. A variable current circuit is coupled between the first and second input terminals of the driver circuit and coupled to the input current sense circuit. The variable current circuit is coupled to conduct a bleeder current between the first and second input terminals in response to the bleeder on/off signal. A current scaling circuit is coupled to the variable current circuit to output a current scale signal which is received by the variable current circuit in response to a shutdown signal. The shutdown signal is representative of a conduction angle.

First claim

What is claimed is:

1. A bleeder circuit, comprising:
an input current sense circuit coupled to one of first and second input terminals of a driver circuit to output a bleeder on/off signal in response to an input current through the first and second input terminals of the driver circuit, wherein the driver circuit is coupled to drive a load;
a variable current circuit coupled between the first and second input terminals of the driver circuit and coupled to the input current sense circuit, wherein the variable current circuit is coupled to conduct a bleeder current between the first and second input terminals in response to the bleeder on/off signal; and
a current scaling circuit coupled to the variable current circuit, wherein the current scaling circuit is coupled to output a current scale signal coupled to be received by the variable current circuit in response to a shutdown signal, wherein the shutdown signal is representative of a conduction angle.

2. The bleeder circuit of claim 1 , wherein the variable current circuit is coupled to increase the bleeder current to a first value in response to the bleeder on/off signal indicating that the input current is less than a threshold current.

3. The bleeder circuit of claim 2 , wherein the threshold current is greater than or equal to a holding current of a dimmer circuit coupled to at least one of the first and second input terminals.

4. The bleeder circuit of claim 2 , wherein the variable current circuit is coupled to the current scaling circuit to increase the bleeder current to a second value in response to the current scale signal indicating a conduction angle is less than a threshold conduction angle.

5. The bleeder circuit of claim 4 , wherein the first value is less than the second value.

6. The bleeder circuit of claim 4 , wherein the input current sense circuit turns the bleeder on/off signal logic high if the input current is lower than the threshold current, and turns the bleeder on/off signal logic low if the input current is equal to or greater than the threshold current.

7. The bleeder circuit of claim 1 , wherein the input current sense circuit includes a current sense resistor coupled to said one of the first and second input terminals of the driver circuit, wherein a voltage drop across the current sense resistor is responsive to the input current.

8. The bleeder circuit of claim 7 , wherein the input current sense circuit includes a current sense transistor coupled to the current sense resistor, wherein the current sense transistor is coupled to turn on in response to the voltage drop across the current sense resistor.

9. The bleeder circuit of claim 8 , wherein the current sense resistor is coupled to a control terminal of the current sense transistor, and coupled to said one of the first and second input terminals of the driver circuit.

10. The bleeder circuit of claim 1 , wherein the current scaling circuit includes a current scale resistor coupled to a diode, wherein the current scale resistor is coupled to receive the shutdown signal, and wherein the diode is coupled to output the current scale signal in response to a voltage drop across the current scale resistor.

11. The bleeder circuit of claim 1 , wherein the variable current circuit comprises a first transistor having a first terminal coupled to said one of the first and second input terminals of the driver circuit, and a second terminal coupled to another one of the first and second input terminals of the driver circuit, wherein a control terminal of the first transistor is coupled to receive the bleeder on/off signal, and further coupled to receive the current scale signal.

12. The bleeder circuit of claim 1 , wherein the input current is conducted through the first and second input terminals of the driver circuit from a dimmer circuit.

13. The bleeder circuit of claim 1 , wherein the shutdown signal is representative of a conduction angle which is representative of a portion of an ac line voltage.

14. The bleeder circuit of claim 1 , wherein the shutdown signal is logic high if a conduction angle is lower than a first threshold, and the shutdown signal is logic low if the conduction angle is greater than or equal to the first threshold.

15. The bleeder circuit of claim 14 , wherein the current scaling circuit is enabled if the shutdown signal is logic high, and the current scaling circuit is disabled if the shutdown signal is logic low.

16. The bleeder circuit of claim 15 , further comprising a bleeder protection circuit, coupled between the first and second input terminals of the driver circuit to receive an input voltage, wherein the bleeder protection circuit comprises a second transistor coupled to output a bleeder bypass signal to the current scaling circuit.

17. The bleeder circuit of claim 16 , wherein the current scaling circuit is coupled to output a logic low current scale signal when the bleeder bypass signal is logic high, and coupled to output a logic high current scale signal when the bleeder bypass signal is logic low.

18. The bleeder protection circuit of claim 16 , wherein the bleeder bypass signal is logic high if the input voltage is equal to or greater than a threshold voltage, and the bleeder bypass signal is logic low if the input voltage is lower than the threshold voltage.

19. A circuit for use in a lighting system, comprising:
a driver circuit having first and second input terminals coupled to conduct an input current, wherein the driver circuit is coupled to drive a load; and
a bleeder circuit, coupled between the first and second input terminals of the driver circuit, the bleeder circuit including:
an input current sense circuit coupled to output a bleeder on/off signal in response to the input current;
a current scaling circuit coupled to output a current scale signal in response to a shutdown signal, the shutdown signal being representative of a conduction angle; and
a variable current circuit coupled to the input current sense circuit to conduct a bleeder current between the first and second input terminals in response to bleeder on/off signal, wherein the variable current circuit is further coupled to the current scale circuit to conduct the bleeder current between the first and second input terminals in response to the current scale signal.

20. The circuit of claim 19 , further comprising a rectifier coupled to the first and second input terminals of the driver circuit.

21. The circuit of claim 19 , wherein the variable current circuit is coupled to increase the bleeder current to a first value in response to the bleeder on/off signal indicating that the input current is less than a threshold current, and wherein the variable current circuit is coupled to increase the bleeder current to a second value in response to the in response to the current scale signal indicating that the conduction angle is less than a first threshold.

22. The circuit of claim 21 , wherein the threshold current is greater than or equal to holding current of a thyristor circuit coupled to at least one of the first and second input terminals of the driver circuit.

23. The circuit of claim 19 , wherein the input current sense circuit comprises a current sense resistor coupled to one of the first and second input terminals of the driver circuit, wherein a voltage drop across the current sense resistor is responsive to the input current, and wherein the input current sense circuit further comprises a current sense transistor coupled

Assignees

• Power Integrations Inc

Inventors

• Vaughan Peter
• Angeles Christian Pura

Classifications

• H05B33/0845

  Electricity · mapped topic

• H05B33/0815

  Electricity · mapped topic

• H05B33/0884 Primary

  Electricity · mapped topic

• H05B45/3575 Primary

  by means of dummy loads or bleeder circuits, e.g. for dimmers · CPC title

• H05B45/3725

  Switched mode power supply [SMPS] · CPC title