DC voltage conversion circuit and liquid crystal display device

• US 10,600,374 B2
• Filed: 11/15/2017
• Issued: 03/24/2020
• Est. Priority Date: 07/18/2017
• Status: Active Grant

• Current Assignee: Shenzhen China Star Optoelectronics Semiconductor Display Technology Co., Ltd. (TCL Technology Group Corp.)
• Original Assignee: Shenzhen China Star Optoelectronics Semiconductor Display Technology Co., Ltd. (TCL Technology Group Corp.)
• Inventors: Zhang, Xianming
• Primary Examiner(s): Edouard, Patrick N
• Assistant Examiner(s): Giles, Eboni N
• Application Number:
  US15/579,934
• Publication Number:
  US 20190027103A1
• Time in Patent Office: 860 Days
• CPC Class Codes: G09G 2320/0204 Compensation of DC component across the pixels in flat panels
• CPC Class Codes: G09G 2330/028 Generation of voltages supplied to electrode drivers in a matrix display other than LCD
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/36 using liquid crystals
• CPC Class Codes: H02M 3/156 with automatic control of output voltage or current, e.g. switching regulators

Abstract

The present invention provides a DC voltage conversion circuit and a liquid crystal display device. The DC voltage conversion circuit comprises a voltage dividing unit, a voltage conversion unit, a first subtractor, an adder, a second subtractor, and a pulse width modulation unit. The pulse width modulation unit is used for correspondingly adjusting the duty ratio of the pulse signal outputted when a voltage outputted from the output terminal of the second subtractor is smaller than or greater than a preset voltage difference, and the output voltage and the feedback voltage are increased or decreased until the voltage outputted from the second subtractor output is equal to the preset voltage difference. So as to increase the output voltage when the output current of the DC voltage conversion circuit is increased, and reduce the output voltage when the output current is decreased, and can ensure that the voltage received by the connected electrical components is consistent and the quality of the product is improved.

Claims

1. A DC voltage conversion circuit, comprising a voltage dividing unit, a voltage conversion unit, a first subtractor, an adder, a second subtractor, and a pulse width modulation unit;

an input terminal of the voltage dividing unit being connected with an input voltage, an output terminal of the voltage dividing unit being electrically connected with an input terminal of the voltage conversion unit, a first output terminal of the voltage conversion unit outputting an output voltage, and a second output terminal of the voltage conversion unit outputting a feedback voltage;

or

an input terminal of the voltage conversion unit being connected with an input voltage, a first output terminal of the voltage conversion unit being electrically connected with an input terminal of the voltage dividing unit, a second output terminal of the voltage conversion unit outputting a feedback voltage, and an output terminal of the voltage dividing unit outputs an output voltage;

a non-inverting input terminal and an inverting input terminal of the first subtractor being respectively electrically connected with the input terminal and the output terminal of the voltage dividing unit, and the output terminal of the first subtractor being electrically connected with a non-inverting input terminal of the adder;

an inverting input terminal of the adder being connected with a first reference voltage, an output terminal of the adder being electrically connected with an inverting input terminal of the second subtractor;

a non-inverting input terminal of the second subtractor being connected with the feedback voltage, an output terminal of the second subtractor being electrically connected with the input terminal of the pulse width modulation unit, wherein the inverting input terminal and the non-inverting input terminal of the second subtractor respectively receive a first signal and a second signal that are respectively determined according to a variable signal from the voltage dividing unit and a variable signal from the voltage conversion unit that is connected to the voltage dividing unit;

the output terminal of the pulse width modulation unit being electrically connected with a control terminal of the voltage conversion unit;

the pulse width modulation unit being used for correspondingly adjusting the duty ratio of the pulse signal outputted when a voltage outputted from the output terminal of the second subtractor is smaller than or greater than a preset voltage difference, and the output voltage and the feedback voltage are increased or decreased until the voltage outputted from the second subtractor output is equal to the preset voltage difference.

2. The DC voltage conversion circuit according to claim 1, wherein the voltage dividing unit is a first resistor, a first terminal of the first resistor is the input terminal of the voltage dividing unit, and a second terminal of the first resistor is the output terminal of the voltage dividing unit.

3. The DC voltage conversion circuit according to claim 1, wherein the voltage conversion unit comprises a switching element, an inductance, a second resistor, a third resistor, and a diode;

an input terminal of the switching element is the input terminal of the voltage conversion unit, the control terminal of the switching element is the control terminal of the voltage conversion unit, an output terminal of the switching element is electrically connected with a first terminal of the inductance;

a second terminal of the inductance is the first terminal of the voltage conversion unit;

a cathode of the diode is electrically connected with the first terminal of the inductance, the anode of the diode is grounded;

a first terminal of the second resistor is electrically connected with the second terminal of the inductance, a second terminal of the second resistor is the second output terminal of the voltage conversion unit and is electrically connected with a first terminal of the third resistor;

a second terminal of the third resistor is grounded.

4. The DC voltage conversion circuit according to claim 3, wherein the switching unit is a field effect transistor, a gate electrode of the field effect transistor is the control terminal of the switching unit, a drain electrode of the field effect transistor is the input terminal of the switching unit, and a source electrode of the field effect transistor is the output terminal of the switching unit.

5. The DC voltage conversion circuit according to claim 4, wherein the field effect transistor is an N-type field effect transistor.

6. The DC voltage conversion circuit according to claim 5, wherein the pulse width modulation unit correspondingly increases the duty ratio of the pulse signal outputted from the output terminal of the pulse width modulation unit, when the voltage outputted from the output terminal of the second subtractor is smaller than the preset voltage difference, the voltage outputted from the output terminal of the voltage conversion unit and the feedback voltage are controlled to be increased until the voltage outputted from the output of the second subtractor is equal to the preset voltage difference;

the pulse width modulation unit correspondingly decreases the duty ratio of the pulse signal outputted from the output terminal of the pulse width modulation unit, when the voltage outputted from the output terminal of the second subtractor is larger than the preset voltage difference, the voltage outputted from the output terminal of the voltage conversion unit and the feedback voltage are controlled to be decreased until the voltage outputted from the output of the second subtractor is equal to the preset voltage difference.

7. The DC voltage conversion circuit according to claim 4, wherein the field effect transistor is a P-type field effect transistor.

8. The DC voltage conversion circuit according to claim 7, wherein the pulse width modulation unit correspondingly decreases the duty ratio of the pulse signal outputted from the output terminal of the pulse width modulation unit, when the voltage outputted from the output terminal of the second subtractor is smaller than the preset voltage difference, the voltage outputted from the output terminal of the voltage conversion unit and the feedback voltage are controlled to be increased until the voltage outputted from the output of the second subtractor is equal to the preset voltage difference;

the pulse width modulation unit correspondingly increases the duty ratio of the pulse signal outputted from the output terminal of the pulse width modulation unit, when the voltage outputted from the output terminal of the second subtractor is larger than the preset voltage difference, the voltage outputted from the output terminal of the voltage conversion unit and the feedback voltage are controlled to be decreased until the voltage outputted from the output of the second subtractor is equal to the preset voltage difference.

9. A liquid crystal display device, comprising the DC voltage conversion circuit according to claim 1.

10. A DC voltage conversion circuit, comprising a voltage dividing unit, a voltage conversion unit, a first subtractor, an adder, a second subtractor, and a pulse width modulation unit;

an input terminal of the voltage dividing unit being connected with an input voltage, an output terminal of the voltage dividing unit being electrically connected with an input terminal of the voltage conversion unit, a first output terminal of the voltage conversion unit outputting an output voltage, and a second output terminal of the voltage conversion unit outputting a feedback voltage;

or

an input terminal of the voltage conversion unit being connected with an input voltage, a first output terminal of the voltage conversion unit being electrically connected with an input terminal of the voltage dividing unit, a second output terminal of the voltage conversion unit outputting a feedback voltage, and an output terminal of the voltage dividing unit outputs an output voltage;

a non-inverting input terminal and an inverting input terminal of the first subtractor being respectively electrically connected with the input terminal and the output terminal of the voltage dividing unit, and the output terminal of the first subtractor being electrically connected with a non-inverting input terminal of the adder;

an inverting input terminal of the adder being connected with a first reference voltage, an output terminal of the adder being electrically connected with an inverting input terminal of the second subtractor;

a non-inverting input terminal of the second subtractor being connected with the feedback voltage, an output terminal of the second subtractor being electrically connected with the input terminal of the pulse width modulation unit, wherein the inverting input terminal and the non-inverting input terminal of the second subtractor respectively receive a first signal and a second signal that are respectively determined according to a variable signal from the voltage dividing unit and a variable signal from the voltage conversion unit that is connected to the voltage dividing unit;

the output terminal of the pulse width modulation unit being electrically connected with a control terminal of the voltage conversion unit;

the pulse width modulation unit being used for correspondingly adjusting the duty ratio of the pulse signal outputted when a voltage outputted from the output terminal of the second subtractor is smaller than or greater than a preset voltage difference, and the output voltage and the feedback voltage are increased or decreased until the voltage outputted from the second subtractor output is equal to the preset voltage difference;

wherein the voltage dividing unit is a first resistor, a first terminal of the first resistor is the input terminal of the voltage dividing unit, and a second terminal of the first resistor is the output terminal of the voltage dividing unit;

wherein the voltage conversion unit comprises a switching element, an inductance, a second resistor, a third resistor, and a diode;

an input terminal of the switching element is the input terminal of the voltage conversion unit, the control terminal of the switching element is the control terminal of the voltage conversion unit, an output terminal of the switching element is electrically connected with a first terminal of the inductance;

a second terminal of the inductance is the first terminal of the voltage conversion unit;

a cathode of the diode is electrically connected with the first terminal of the inductance, the anode of the diode is grounded;

a first terminal of the second resistor is electrically connected with the second terminal of the inductance, a second terminal of the second resistor is the second output terminal of the voltage conversion unit and is electrically connected with a first terminal of the third resistor;

a second terminal of the third resistor is grounded;

wherein the switching unit is a field effect transistor, a gate electrode of the field effect transistor is the control terminal of the switching unit, a drain electrode of the field effect transistor is the input terminal of the switching unit, and a source electrode of the field effect transistor is the output terminal of the switching unit;

wherein the field effect transistor is an N-type field effect transistor.

11. The DC voltage conversion circuit according to claim 10, wherein the pulse width modulation unit correspondingly increases the duty ratio of the pulse signal outputted from the output terminal of the pulse width modulation unit, when the voltage outputted from the output terminal of the second subtractor is smaller than the preset voltage difference, the voltage outputted from the output terminal of the voltage conversion unit and the feedback voltage are controlled to be increased until the voltage outputted from the output of the second subtractor is equal to the preset voltage difference;

the pulse width modulation unit correspondingly decreases the duty ratio of the pulse signal outputted from the output terminal of the pulse width modulation unit, when the voltage outputted from the output terminal of the second subtractor is larger than the preset voltage difference, the voltage outputted from the output terminal of the voltage conversion unit and the feedback voltage are controlled to be decreased until the voltage outputted from the output of the second subtractor is equal to the preset voltage difference.