AC-DC single-inductor multiple-output LED drivers

• US 10,212,770 B2
• Filed: 04/23/2015
• Issued: 02/19/2019
• Est. Priority Date: 04/23/2015
• Status: Active Grant

• Current Assignee: Versitech Limited (Government of Hong Kong Special Administrative Region)
• Original Assignee: Versitech Limited (Government of Hong Kong Special Administrative Region)
• Inventors: Guo, Yue, Lee, Ting Leung Albert, Li, Sinan, Tan, Siew Chong, Lee, Chi Kwan, Hui, Shu Yuen
• Primary Examiner(s): Le, Tung X
• Application Number:
  US15/566,564
• Publication Number:
  US 20180092179A1
• Time in Patent Office: 1,398 Days
• Field of Search: 315186, 315192, 315193
• CPC Class Codes: H02M 1/009 having two or more independently controlled outputs for DC-DC converter with intermediate AC H02M3/33561
• CPC Class Codes: H02M 1/14 Arrangements for reducing ripples from dc input or output
• CPC Class Codes: H02M 1/42 Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators
• CPC Class Codes: H02M 3/158 including plural semiconductor devices as final control devices for a single load
• CPC Class Codes: H02M 7/06 using discharge tubes without control electrode or semiconductor devices without control electrode
• CPC Class Codes: H05B 45/24 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/375 using buck topology
• 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]

Abstract

A single-stage AC-DC single-inductor multiple-output (SIMO) LED driver uses a single inductor (L) to drive multiple independent LED strings (34₁-34_n) with Power Factor Correction (PFC). The driver uses a diode bridge (20) to achieve initial AC to DC conversion. The output of the bridge (20) is provided to a buck converter whose output is shared with multiple LED strings by a time division multiplex circuit. Feedback is used to separately control the current supplied to each LED string by using a separate reference for each string and controlling the width of the current pulse provided to a string. Current balancing in every LED string can be achieved with the same voltage reference without the need for additional circuitry.

Claims

1. A single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver comprising:

an AC-DC rectifier circuit;

a DC-DC converter that receives the output of the rectifier circuit and passes the rectifier output through an input switching circuit and an inductor to an output of the driver, said converter circuit including a control circuit which produces a control signal that causes the input switching circuit to alternately open and close;

an output switching circuit that sequentially connects the output of the inductor to respective individual strings of LEDs in round robin fashion;

comparator circuits that compare the current in an LED string to a reference, and set the period of time during which the output switching circuit connects the inductor to the respective string of LEDs based on the comparison so as to maintain a current level in the LED string; and

a multiplexer circuit that multiplexes the outputs of the comparator circuits into a single signal y,

wherein the control circuit for the switching circuit includes a first divider for providing a portion of the output of the rectifier circuit, a squaring circuit for squaring the portion of the output of the rectifier circuit to produce a signal x, and a second divider circuit for dividing the y signal by the x signal to produce the control signal for the switching circuit so that the effect of a change in input AC to the rectifier circuit has a reduced effect on the DC operating point of the driver.

2. The single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver of claim 1, wherein the DC-DC converter is a buck converter that includes a diode between ground and the junction of the switching circuit and the inductor.

3. The single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver of claim 1, wherein the current supplied to each LED string is controlled by using a separate reference for each string and controlling the width of the current pulse provided to a string from the inductor.

4. The single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver of claim 3, wherein the reference in each string is the same and the current in every LED string is the same.

5. The single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver of claim 3, wherein the reference in each string is configured to be different so that the current in each string is different.

6. The single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver of claim 1, with Power Factor Correction (PFC).

7. The single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver of claim 1, wherein the rectifier circuit is a full wave bridge rectifier with a capacitor across its output to reduce ripple.

8. The single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver of claim 1, further including a pulse width modulator driven by a cyclic waveform and the y divided by x signal, the output of such pulse width modulator determining the duty cycle of the switching circuit.

9. The single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver of claim 1, further including proportional integrator compensators between each comparator and the multiplexer.

10. The single-stage AC-DC single-inductor multiple-output (SIMO) light emitting diode (LED) driver of claim 1, wherein the input switching circuit includes a first switch connecting and disconnecting the output of the rectifier circuit with the inductor and a second switch connecting and disconnection the output of the rectifier circuit with ground, said switches operating during a single cycle of supplying current to an LED string in a discontinuous mode such that in a first mode the first switch is closed and the second switch is open, in a second mode the first switch is open and the second switch is closed and in a third mode both the first and second switch are open to create an idle period when there is no inductor current, whereby cross-interference among LED strings is reduced.