Patent ID: 9155136
Filing Date: 2015-10-06
Classification: H05B

Abstract:
1. A light emitting diode (LED) driver receiving an input voltage, driving a first and a second LED modules, and comprising: a compensation capacitor set including a first and a second capacitors electrically connected to each other in series, wherein the first capacitor is electrically connected to the first and the second LED modules, the second capacitor is grounded, and the compensation capacitor set provides a compensation voltage to the first and the second LED modules when an instantaneous voltage value of the input voltage is lower than an LED conduction voltage such that the first and the second LED modules are conductible; an overvoltage protection and energy recovery circuit, including: an energy recovery circuit, including: a third capacitor having a first and a second terminals; and a first diode having an anode and a cathode, wherein the anode of the first diode is electrically connected to the first terminal of the third capacitor, the second terminal of the third capacitor is grounded, the cathode of the first diode is electrically connected to the first and the second LED modules, and a stored energy in the third capacitor is released to the first and the second LED modules when a cross voltage between the first and the second terminals of the third capacitor is larger than a cross voltage of the compensation capacitor set; and a segmental current-limiting circuit, including: a first voltage divider electrically connected to the compensation capacitor set in parallel and having a first midpoint; a first current limiting circuit, including: a second diode having an anode and a cathode; a first resistor having a first and a second terminals, wherein the first terminal of the first resistor is electrically connected to the anode of the second diode, and the second terminal of the first resistor is grounded; a first transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal of the first transistor is electrically connected to the first and the second LED modules, the second terminal of the first transistor is electrically connected to the first terminal of the first resistor, and the control terminal of the first transistor is electrically connected to the first midpoint of the first voltage divider; and a second transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal of the second transistor is electrically connected to the second terminal of the first transistor, the second terminal of the second transistor is grounded, and the control terminal of the second transistor is electrically connected to the cathode of the second diode; and an input voltage detection circuit electrically connected to the compensation capacitor set in parallel and including a second midpoint electrically connected to the control terminal of the second transistor, wherein the second midpoint has a voltage value used to determine whether the LED driver enters a segmental conduction mode.