CIRCUIT AND METHOD FOR DETECTING FAULTY DIODE

• US 20100289518A1
• Filed: 12/07/2009
• Published: 11/18/2010
• Est. Priority Date: 05/15/2009
• Status: Active Grant

• Current Assignee: ENE Technology, Inc.
• Original Assignee: ENE Technology, Inc.
• Inventors: Huang, Chi-Feng
• Granted Patent: US 7,965,096 B2
• Time in Patent Office: Days
• US Class Current: 324/767
• CPC Class Codes: G01R 31/2635 Testing light-emitting diodes, laser diodes or photodiodes

Abstract

A circuit for detecting faulty diode is disclosed, wherein the circuit for detecting faulty diode comprises a diode having an anode connecting to a voltage supply; a first switch having a first end connected to a cathode of the diode; a testing current source connected to the second end of the first switch; a one-shot circuit connected to a control end of the first switch, by which an output signal is generated and transmitted to the control end; and a comparator connected to a reference voltage input terminal for receiving a reference voltage and connected to the second end of the first switch. When the one-shot circuit closes the first switch for a maintaining period to urge the comparator comparing the reference voltage with the voltage applied to the second end of the first switch, whereby a signal used to discriminate whether the diode is fail or not is generated.

Claims

1. A circuit for detecting faulty diode comprising:

a diode, having an anode connecting to a voltage supply;

a first switch, having a first end connected to a cathode of the diode;

a testing current source, connected to a second end of the first switch;

an one-shot circuit, used to generated and transmitted an output signal to a control end of the first switch; and

a comparator, having two ends respectively connected to a reference voltage input terminal for receiving a reference voltage and connected to the second end of the first switch;

wherein when the one-shot circuit closes the first switch for a maintaining period to urge the comparator comparing the reference voltage with the voltage applied to the second end of the first switch, whereby a signal used to discriminate whether the diode is fail or not is generated.

2. The circuit for detecting faulty diode according to claim 1, further comprising:

a second switch, having a first end connected to the cathode of the diode; and

a control current source, connected to a second end of the second switch;

wherein after the one-shot circuit closes the first switch for the maintaining period, the second switch is closed and the first switch is opened, whereby the control current source controls the diode.

3. The circuit for detecting faulty diode according to claim 1, wherein the diode is a light emitting diode (LED).

4. The circuit for detecting faulty diode according to claim 1, wherein the maintaining period is less than 1 millisecond (ms).

5. The circuit for detecting faulty diode according to claim 1, wherein the reference voltage applied to the reference voltage input terminal is an open-testing voltage or a short-testing voltage.

6. The circuit for detecting faulty diode according to claim 5, wherein the maintaining period further comprises a short-testing period and an open-testing period;

wherein during the short-testing period the short-testing voltage is applied as the reference voltage; and

during the open-testing period the open-testing voltage is applied as the reference voltage.

7. A method for detecting faulty diode comprising:

adopting a detecting mode to switch a testing current source connecting with a diode, so as to provide a testing current flowing through a diode, whereby the existence of any faulty diode can be discriminated in accordance with a bias voltage of the diode; and

adopting an operating mode to switch a control current source connecting with the diode, so as to provide a control current flowing through the diode;

wherein after the detecting mode is hold for a maintaining period, the operating mode regains its dominance, and the maintaining period is less than 1 ms.

8. The method for detecting faulty diode according to claim 7, wherein the maintaining period is determined by a one-shot circuit.

9. The method for detecting faulty diode according to claim 7, wherein the maintaining period further comprises a short-testing period and an open-testing period.

10. The method for detecting faulty diode according to claim 7, wherein the diode is a LED

11. The method for detecting faulty diode according to claim 10, wherein when the control current flowing through the LED, the LED can generate a light signal.