US-12628255-B2 - Driving device and driving method for light- emitting element

US12628255B2US 12628255 B2US12628255 B2US 12628255B2US-12628255-B2

Abstract

The disclosure provides a driving device and a driving method for a light-emitting element. The driving device includes a driving circuit, a softstart circuit, and a capacitor. An output terminal of the softstart circuit is coupled to the capacitor and the driving circuit to provide a dimming voltage. A driving signal output by the driving circuit drives a light-emitting element circuit. The driving circuit is enabled or disabled based on an enabling signal. Based on a relationship between the dimming voltage and current information of the light-emitting element circuit, the driving circuit dynamically adjusts a duty cycle of the driving signal. In response to the enabling signal disabling the driving circuit, the softstart circuit pulls down an original adjustment voltage to generate a pulled-down voltage as the dimming voltage. In response to the enabling signal enabling the driving circuit, the softstart circuit pulls up the dimming voltage.

Inventors

Chih-Hsiang Wu

Assignees

QISDA CORPORATION

Dates

Publication Date: 20260512
Application Date: 20240517
Priority Date: 20230630

Claims (7)

1 . A driving device for a light-emitting element, comprising: a driving circuit, adapted to output a driving signal to drive a light-emitting element circuit, wherein the driving circuit is enabled or disabled based on an enabling signal, and the driving circuit dynamically adjusts a duty cycle of the driving signal based on a relationship between a dimming voltage and current information of the light-emitting element circuit; a softstart circuit, having an output terminal coupled to the driving circuit to provide the dimming voltage, wherein the softstart circuit pulls down an original adjustment voltage to generate a pulled-down voltage as the dimming voltage in response to the enabling signal disabling the driving circuit, and the softstart circuit pulls up the dimming voltage in response to the enabling signal enabling the driving circuit; and a first capacitor, coupled to the output terminal of the softstart circuit, wherein the softstart circuit comprises: a first resistor, having a first terminal adapted to receive the original adjustment voltage, wherein a second terminal of the first resistor is coupled to the output terminal of the softstart circuit; and a variable resistor circuit, coupled between the second terminal of the first resistor and a first reference voltage, wherein the variable resistor circuit reduces a resistance of the variable resistor circuit in response to the enabling signal disabling the driving circuit, and the variable resistor circuit increases the resistance of the variable resistor circuit in response to the enabling signal enabling the driving circuit.
2 . The driving device according to claim 1 , wherein the variable resistor circuit comprises: a second resistor, having a first terminal coupled to the second terminal of the first resistor, wherein a second terminal of the second resistor is coupled to the first reference voltage; and a shunt circuit, coupled to the second terminal of the first resistor, wherein the shunt circuit provides a shunt path to the second terminal of the first resistor in response to the enabling signal disabling the driving circuit, and the shunt circuit turns off the shunt path in response to the enabling signal enabling the driving circuit.
3 . The driving device according to claim 2 , wherein the shunt circuit comprises: a third resistor, having a first terminal coupled to the second terminal of the first resistor; and a switch circuit, coupled between a second terminal of the third resistor and the first reference voltage, wherein the switch circuit is turned on in response to the enabling signal disabling the driving circuit, and the switch circuit is turned off in response to the enabling signal enabling the driving circuit.
4 . The driving device according to claim 3 , wherein the switch circuit comprises: a first switch, having a first terminal coupled to the second terminal of the third resistor, wherein a second terminal of the first switch is coupled to the first reference voltage; and a control circuit, coupled to a control terminal of the first switch, wherein the control circuit turns on the first switch in response to the enabling signal disabling the driving circuit, and the control circuit turns off the first switch in response to the enabling signal enabling the driving circuit.
5 . The driving device according to claim 4 , wherein the control circuit comprises: a fourth resistor, having a first terminal coupled to a power supply voltage, wherein a second terminal of the fourth resistor is coupled to the control terminal of the first switch; and a second switch, having a first terminal coupled to the control terminal of the first switch, wherein a second terminal of the second switch is coupled to a second reference voltage, the second switch is turned off in response to the enabling signal disabling the driving circuit, and the second switch is turned on in response to the enabling signal enabling the driving circuit.
6 . The driving device according to claim 5 , wherein the control circuit further comprises: a fifth resistor, having a first terminal coupled to the second terminal of the fourth resistor, wherein a second terminal of the fifth resistor is coupled to a third reference voltage; a sixth resistor, having a first terminal adapted to receive the enabling signal, wherein a second terminal of the sixth resistor is coupled to a control terminal of the second switch; and a seventh resistor, having a first terminal coupled to the second terminal of the sixth resistor, wherein a second terminal of the seventh resistor is coupled to a fourth reference voltage.
7 . A driving method for a light-emitting element, comprising: enabling or disabling a driving circuit by an enabling signal; dynamically adjusting a duty cycle of a driving signal by the driving circuit based on a relationship between a dimming voltage and current information of a light-emitting element circuit, wherein an output terminal of a softstart circuit is coupled to the driving circuit to provide the dimming voltage; outputting the driving signal by the driving circuit to drive the light-emitting element circuit; pulling down an original adjustment voltage to generate a pulled-down voltage as the dimming voltage by the softstart circuit in response to the enabling signal disabling the driving circuit; pulling up the dimming voltage by the softstart circuit in response to the enabling signal enabling the driving circuit, wherein a first capacitor is coupled to the output terminal of the softstart circuit; reducing a resistance of a variable resistor circuit by the variable resistor circuit of the softstart circuit in response to the enabling signal disabling the driving circuit, wherein a first terminal of a first resistor of the softstart circuit receives the original adjustment voltage, a second terminal of the first resistor is coupled to the driving circuit to provide the dimming voltage, and the variable resistor circuit is coupled between the second terminal of the first resistor and a reference voltage; and increasing the resistance of the variable resistor circuit by the variable resistor circuit in response to the enabling signal enabling the driving circuit.

Description

CROSS-REFERENCE TO RELATED APPLICATION This application claims the priority benefit of China application serial no. 202310792827.X, filed on Jun. 30, 2023. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. BACKGROUND Technical Field The disclosure relates to an electronic circuit, and in particular, to a driving device and a driving method for a light-emitting element. Description of Related Art A light source of a projector develops from a single light source to a multi-color (such as red, green, blue) light source. The projector uses pulse width modulation (PWM) dimming technology to adjust a current of the light source so as to adjust brightness and color. Therefore, current stability is important for light source startup. An overshoot current often occurs when activating a light source quickly. The overshoot current often exceeds a rated current value. The overshoot current that exceeds the design value will not only reflect instability in the brightness/color of the light source, but may also burn out the light source elements. SUMMARY The disclosure provides a driving device and a driving method for a light-emitting element to reduce an overshoot current when activating the light-emitting element. In an embodiment of the disclosure, the driving device includes a driving circuit, a softstart circuit, and a first capacitor. The driving circuit is adapted to output a driving signal to drive a light-emitting element circuit. The driving circuit is enabled or disabled based on an enabling signal. Based on a relationship between a dimming voltage and current information of the light-emitting element circuit, the driving circuit dynamically adjusts a duty cycle of the driving signal. An output terminal of the softstart circuit is coupled to the driving circuit to provide the dimming voltage. In response to the enabling signal disabling the driving circuit, the softstart circuit pulls down an original adjustment voltage to generate a pulled-down voltage as the dimming voltage. In response to the enabling signal enabling the driving circuit, the softstart circuit pulls up the dimming voltage. The first capacitor is coupled to the output terminal of the softstart circuit. In an embodiment of the disclosure, the driving method includes the following steps. A driving circuit is enabled or disabled by an enabling signal. Based on a relationship between a dimming voltage and current information of a light-emitting element circuit, a duty cycle of a driving signal is dynamically adjusted by the driving circuit. An output terminal of a softstart circuit is coupled to the driving circuit to provide the dimming voltage. The driving signal is output by the driving circuit to drive the light-emitting element circuit. In response to the enabling signal disabling the driving circuit, the softstart circuit pulls down an original adjustment voltage to generate a pulled-down voltage as the dimming voltage. In response to the enabling signal enabling the driving circuit, the softstart circuit pulls up the dimming voltage. A first capacitor is coupled to the output terminal of the softstart circuit. Based on the above, when the enabling signal disables the driving circuit, the softstart circuit generates a pulled-down voltage lower than the original adjustment voltage, and uses the pulled-down voltage as the dimming voltage provided to the driving circuit. When the enabling signal enables the driving circuit, the softstart circuit slowly pulls up the dimming voltage from a level of the pulled-down voltage to approximately a level of the original adjustment voltage. After the enabling signal enables the driving circuit, the driving circuit can dynamically adjust the duty cycle of the driving signal based on the relationship between the dimming voltage and the current information of the light-emitting element circuit, so that the current of the light-emitting element can be dynamically adjusted. During the process of enabling/activating the driving circuit, since the dimming voltage is slowly pulled up to approximately the level of the original adjustment voltage, the overshoot current of the light-emitting element can be effectively reduced when starting up the light-emitting element. In order to make the above-mentioned features and advantages of the disclosure clearer and easier to understand, the following embodiments are given and described in details with accompanying drawings as follows. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit block diagram of a driving device for a light-emitting element according to an embodiment. FIG. 2 is a schematic diagram of a situation in which an overshoot current occurs when a light-emitting element circuit is quickly activated according to an embodiment. FIG. 3 is a schematic circuit block diagram of a driving device for a light-emitting element according to an embodiment of the disclos