Dimming driver circuit and control method thereof

Patent metadata

Field	Value
Publication number	US-10426005-B2
Application number	US-201715489207-A
Country	US
Kind code	B2
Filing date	Apr 17, 2017
Priority date	May 4, 2016
Publication date	Sep 24, 2019
Grant date	Sep 24, 2019

Abstract

A control method for a dimming driver circuit is provided. Firstly, a detecting signal is generated according to a result of detecting a parameter of a power converting unit. Then, the dimming current is compared with a preset current threshold value. If the dimming current is higher than the preset current threshold value, a status information of a switch element of the power converting unit is determined according to the detecting signal, and a first setting is defined. If the dimming current is lower than or equal to the preset current threshold value, the status is determined according to the detecting signal, a pulse ratio in a chopping cycle is calculated, and a second setting is defined. According to the first setting or the second setting, an initial control signal is adjusted to a real control signal to control the switch element.

First claim

What is claimed is:

1. A control method for a dimming driver circuit, the dimming driver circuit being configured for adjusting brightness of a light emitting diode, the dimming driver circuit comprising a power converting unit, the power converting unit comprising a switch element, the switching element being alternately turned on or turned off in plural switching cycles during a switching operation, the control method comprising steps of:
(a) previously defining an initial control signal composed of plural pulses, wherein the plural pulses are generated at a pulse frequency, and the switch element is turned on in the switching cycle corresponding to each pulse;
(b) generating at least one detecting signal according to a result of detecting at least one parameter of the power converting unit;
(c) receiving and processing a dimming signal by a control unit of a dimming driver circuit, thereby generating a corresponding dimming current stored in the control unit;
(d) comparing the dimming current with a preset current threshold value;
(e) defining a first setting or a second setting according to a comparing result of the step (d), wherein when the dimming current is higher than the preset current threshold value, a status information of the switch element in each switching cycle is determined according to the at least one detecting signal and a first setting process, so that the first setting is defined, wherein when the dimming current is lower than or equal to the preset current threshold value, the status information of the switch element in each switching cycle is determined according to the at least one detecting signal and a second setting process, the switching operation of the switch element is divided into plural chopping cycles, and a pulse ratio in at least one chopping cycle is calculated according to the dimming current and the preset current threshold value, so that the second setting is defined; and
(f) adjusting the plural pulses of the initial control signal according to the first setting or the second setting, so that a corresponding real control signal is generated, wherein the switching operation of the switch element is controlled according to the real control signal, and an output current corresponding to the dimming signal is generated from the power converting unit to the light emitting diode so as to control the brightness of the light emitting diode.

2. The control method according to claim 1 , wherein the power converting unit comprises:
an input side for receiving an input voltage, wherein the input side comprises a positive input terminal and a negative input terminal;
an output side for outputting an output voltage, wherein the output side comprises a positive output terminal and a negative output terminal;
a diode, wherein a cathode of the diode is electrically connected with the positive input terminal and the positive output terminal;
a capacitor, wherein a first end of the capacitor is electrically connected with the positive input terminal, the positive output terminal and the cathode of the diode;
the switch element comprising a first conduction terminal, a second conduction terminal and a control terminal, wherein the first conduction terminal is electrically connected with the negative input terminal, and the control terminal is electrically connected with a low-side driving unit of the dimming driver circuit; and
a first inductor, wherein a first end of the first inductor is electrically connected with an anode of the diode and the second conduction terminal, and a second end of the first inductor is electrically connected with a second end of the capacitor and the negative output terminal.

3. The control method according to claim 2 , wherein the step (b) comprises sub-steps of:
generating a first detecting signal according to a result of detecting a voltage value of the input voltage; and
generating a second detecting signal according to a result of detecting a voltage value of the output voltage,
wherein the at least one parameter comprises the input voltage and the output voltage, and the at least one detecting signal comprises the first detecting signal and the second detecting signal.

4. The control method according to claim 3 , wherein the status information contains an on time period of the switch element in the switching cycle, wherein in the first setting process, the on time period of the switch element in the switching cycle is calculated according to the first detecting signal, the second detecting signal and the dimming current.

5. The control method according to claim 4 , wherein in the second setting process, the on time period of the switch element in the switching cycle is calculated according to the first detecting signal, the second detecting signal and the preset current threshold value.

6. The control method according to claim 4 , wherein in the first setting process, the on time period is calculated by the following formula:

Ton
=

Idim
⨯

2
⨯
L

VinAD
-
VoutAD

⨯

1
fs

1
+

(

VinAD
-
VoutAD

)

VoutAD

where, Ton is the on time period, Idim is the dimming current, VinAD is the first detecting signal, and VoutAD is the second detecting signal, fs is the pulse frequency, and L is an inductance of the first inductor.

7. The control method according to claim 2 , wherein the step (b) further comprises a sub-step of outputting the at least one detecting signal according to a result of detecting an inductor current of the first inductor, wherein the at least one parameter further contains the inductor current.

8. The control method according to claim 7 , wherein the status information denotes an on state and an off state of the switch element in each switching cycle, wherein in the first setting process, the switch element is switched from the off state to the on state when the detecting signal is equal to a first preset value, and the switch element is switched from the on state to the off state when the detecting signal is equal to a second preset value.

9. The control method according to claim 8 , wherein the first preset value is zero, and the second preset value is two times of the dimming current.

10. The control method according to claim 7 , wherein the status information denotes an on state and an off state of the switch element in each switching cycle, wherein in the second setting process, the switch element is switched from the off state to the on state when the detecting signal is equal to the first preset value, and the switch element is switched from the on state to the off state when the detecting signal is equal to two times of the preset current threshold value.

Assignees

• Delta Electronics Shanghai Co

Inventors

• Fu Xiaoping
• Zhang Xinghua

Classifications

• H02M3/156 Primary

  with automatic control of output voltage or current, e.g. switching regulators · CPC title

• H05B45/10

  Controlling the intensity of the light · CPC title

• H02M1/08

  Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters · CPC title

• H05B33/0818 Primary

  Electricity · mapped topic

• H05B33/0851

  Electricity · mapped topic