CONTROL METHODS AND POWER CONVERTERS SUITABLE FOR TRIAC DIMMING

• US 20150359054A1
• Filed: 05/29/2015
• Published: 12/10/2015
• Est. Priority Date: 06/05/2014
• Status: Active Grant

• Current Assignee: Leadtrend Technology Corporation
• Original Assignee: Leadtrend Technology Corporation
• Inventors: Lin, Chang Yi, Huang, Kuo Chien, Chen, Chi Pin
• Granted Patent: US 9,723,664 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/385 using flyback topology

Abstract

Control methods and apparatuses providing a holding current for a TRIAC dimmer are disclosed. A control method is suitable for a power controller powered by an operation power source. A high-voltage device in the power controller is connected between the operation power source and an input power source, from which the high-voltage device drains a conduction current. An operation voltage of the operation power source is detected, and, when it is below a first reference, the conduction current is forwarded to charge the operation power source. A detected voltage representing an input voltage of the input power source is provided, and if the detected voltage is below a second reference, the conduction current is forwarded to a ground line instead of charging the operation power source.

Claims

1. A control method suitable for a power controller powered by an operation power source, wherein the power controller includes a high-voltage device connected between the operation power source and an input power source, the control method comprising:

detecting an operation voltage of the operation power source;

controlling the high-voltage device to drain a conduction current from the input power source;

forwarding the conduction current to the operation power source for charging the operation power source when the operation voltage is below a first reference;

providing a detected voltage representing an input voltage of the input power source;

comparing the detected voltage with a second reference; and

when the detected voltage is below the second reference, forwarding the conduction current to a ground line, instead of charging the operation power source.

2. The control method of claim 1, further comprising:

providing a transformer with a primary winding, a second winding and an auxiliary winding;

electrically coupling the primary winding to the input power source; and

connecting a voltage divider in parallel with the auxiliary winding, wherein the voltage divider comprises two resistors connected in series through a joint node; and

providing the second reference based on a joint voltage at the joint node.

3. The control method of claim 2, wherein the power controller is a pulse-width modulator capable of providing a PWM signal to control a primary-winding current flowing through the primary winding.

4. The control method of claim 1, further comprising:

generating a discharging current when the conduction current occurs, wherein the discharge current is more than the conduction and drains from the input power source to the ground line.

5. The control method of claim 4, wherein the discharge current is controlled by a bipolar junction transistor, and the conduction current substantially passes through a base of the bipolar junction transistor.

6. The control method of claim 1, further comprising:

connecting two resistors between the high-voltage device and the ground line; and

providing the detected voltage based on a voltage at a joint between the two resistors;

wherein the high-voltage device has a terminal connected to the input power source via another resistor.

7. A power converter suitable for converting an input power source into an output power source, the power converter comprising:

a power controller powered by an operation power source with an operation voltage, comprising;

a high-voltage pin coupled to the input power source;

a high-voltage device capable of draining a conduction current from the input power source via the high-voltage pin;

a high-voltage startup control circuit, for detecting the operation voltage;

a cutoff-time detection circuit for detecting an input voltage of the input power source, and

a demultiplexer coupled to the high-voltage device, the high-voltage startup control circuit and the cutoff-time detection circuit, for forwarding the conduction current to the operation power source when the operation voltage is below a first reference and to a ground line when the input voltage is below a second reference.

8. The power converter of claim 7, wherein the cutoff-time detection circuit comprises two resistors connected in series between the high-voltage pin and the ground line.

9. The power converter of claim 7, further comprising:

a transformer with a primary winding, a secondary winding, and an auxiliary winding; and

two resistors connected in series via a joint, and between two ends of the auxiliary winding;

wherein the power controller comprises a resistance detector coupled to the joint for providing the second reference.

10. The power converter of claim 9, wherein the power controller is a pulse-width modulator providing a PWM signal to a power switch controlling a primary-winding current through the primary winding.

11. The power converter of claim 9, wherein the input power source is an alternating-current input power source, the power converter further comprising:

a bridge rectifier, for rectifying the input power source to provide a direct-current voltage power line coupled to the primary winding.

12. The power converter of claim 7, further comprising:

a current-limiting resistor, connected between the high-voltage pin and the input power source.

13. The power converter of claim 12, further comprising:

a bipolar junction transistor with a base, an emitter, and a collector;

wherein the base and the collector are coupled to two ends of the current-limiting resistor respectively, and the collector is coupled to the ground line.

14. The power converter of claim 7, further comprising:

a TRIAC dimmer coupled to receive an alternating-current power source and to output the input power source.