HIGH EFFICIENCY CONSTANT CURRENT LED DRIVER

• US 20110080102A1
• Filed: 10/01/2010
• Published: 04/07/2011
• Est. Priority Date: 10/01/2009
• Status: Abandoned Application

• Current Assignee: Inventronics (Hangzhou), Inc.
• Original Assignee: Inventronics (Hangzhou), Inc.
• Inventors: Yao, Xiaoli, Ge, Liangan, Hua, Guichao
• Application Number:
  US12/896,346
• Publication Number:
  US 20110080102A1
• Time in Patent Office: Days
• US Class Current: 315/200.R
• CPC Class Codes: H02M 1/0064 Magnetic structures combining different functions, e.g. storage, filtering or transformation
• CPC Class Codes: H02M 1/007 Plural converter units in cascade push-pull DC/DC converters with pre-regulator H02M3/3374; DC-AC converters following a DC-DC stage including a high frequency transformer H02M7/4807; DC-AC converters following a DC-DC conversion stage generating periodically varying voltages H02M7/4826
• CPC Class Codes: H02M 1/4225 using a non-isolated boost converter
• CPC Class Codes: H02M 3/01 Resonant DC/DC converters
• CPC Class Codes: H02M 3/33571 Half-bridge at primary side of an isolation transformer
• CPC Class Codes: H05B 45/355 Power factor correction [PFC]; Reactive power compensation
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The present invention discloses a high efficiency constant current LED driver, which comprises a rectification bridge, a PFC main circuit, an isolated DC/DC converter, a PFC controller and a PFC bus control circuit. Since the input voltage is an intermediate PFC bus voltage, which varies with the output voltage of the DC/DC converter. When the isolated DC/DC converter is an LLC resonant circuit, the operating frequency of the LLC circuit is close to the resonant frequency within a wide output voltage range. Thus, the gain range and the operating frequency is narrow, and can enable the constant current module to work with a high efficiency at a wide output voltage range. When the isolated DC/DC converter is a symmetric half bridge, or an asymmetric half bridge or a full bridge circuit, the duty cycle of DC/DC circuit is close to 50% within a wide output voltage range. Thus, the changing range of the duty cycle of the DC/DC converter will be narrow and can improve the efficiency dramatically.

Claims

1. A circuit which can improve a power factor of a power supply at a light load, the circuit comprising

a filter configured with at least one filter capacitor;

a light load detecting circuit;

a light load;

a logic control and power drive circuit;

a switching transistor;

a rectifier bridge; and

a power factor correction circuit;

wherein the filter is configured to be placed before and/or after the rectifier bridge, the light load detecting circuit is configured to output a control signal to the logic control and power drive circuit which controls the switching transistor to conduct at heavy load and to cut off at light load in order to control a working status of the filter capacitor.

2. The circuit according to claim 1, wherein input terminals of the rectifier bridge are connected with a power line voltage, while output terminals of the rectifier bridge are connected in parallel with the power factor correction circuit and a branch circuit in which a capacitor and the switching transistor are connected in series.

3. The circuit according to claim 2, wherein an output of the light load detecting circuit is connected with an input of the logic control and power drive circuit, and an output of the logic control and power drive circuit is connected with a third terminal of the switching transistor.

4. The circuit according to claim 1, wherein the filter further comprises a second capacitor and an inductor with two terminals of a power line voltage is connected with an input terminal of the rectifier bridge, a positive output of the rectifier bridge is connected with one terminal of the inductor and one terminal of the first capacitor, another terminal of the inductor is connected with one terminal of the second capacitor and the positive input terminal of the power factor correction circuit, while a negative input terminal of the power factor correction circuit is connected to ground.

5. The circuit according to claim 4, wherein another terminal of the second capacitor is connected with a second terminal of the switching transistor, a first terminal of the switching transistor is connected to ground, an output terminal of the light load detecting circuit is connected with an input terminal of the logic control and power drive circuit, and an output of the logic control and power drive circuit is connected with a third terminal of the switching transistor.

6. The circuit according to claim 1, wherein the capacitor in the filter is connected in series with a switching transistor to constitute a series loop, two terminals of the series loop are connected in parallel with a power line, the rectifier bridge is connected in parallel with the power line, output terminals of the rectifier bridge are connected with the power factor correction circuit, an output terminal of the light load detecting circuit is connected to the input of the logic control and power drive circuit, and an output of the logic control and power drive circuit is connected with a third terminal of the switching transistor.