CN111698812B

CN111698812B - Voltage compensation driving circuit

Info

Publication number: CN111698812B
Application number: CN201910144858.8A
Authority: CN
Inventors: 詹子增
Original assignee: Acer Inc
Current assignee: Acer Inc
Priority date: 2019-02-27
Filing date: 2019-02-27
Publication date: 2022-10-21
Anticipated expiration: 2039-02-27
Also published as: CN111698812A

Abstract

The invention provides a voltage compensation driving circuit. The voltage compensation driving circuit converts an input power supply into an output power supply and an auxiliary power supply. The voltage compensation driving circuit provides a boost control signal according to the output current of the output power supply, and the boost control signal has a duty cycle corresponding to the current value of the output current. The voltage compensation driving circuit boosts the auxiliary power supply through the boost control signal to generate a compensation voltage, and transmits the compensation voltage to the light emitting element string through the boost resistor, thereby linearly controlling the brightness of the light emitting element string.

Description

Voltage compensation driving circuit

Technical Field

The present disclosure relates to driving devices, and particularly to a voltage compensation driving circuit.

Background

Current Light-emitting device products, such as Light-emitting diode (LED) products, are required to have a dimming function to adjust the brightness of the Light-emitting device product. Generally, adjusting the brightness of the light emitting device product can be increasing the current of the light emitting device or decreasing the current of the light emitting device.

However, since the input power is a fixed power, increasing the current of the light emitting element affects the output voltage of the driving circuit of the light emitting element product. For example, the current of the light emitting device is increased, and the voltage drop of the output voltage is increased, which means that the voltage value for driving the light emitting device is decreased. Therefore, the brightness of the light emitting device cannot be increased to keep up with the increase of the current, and the light emitting device cannot linearly adjust the brightness according to the adjustment of the current value.

Disclosure of Invention

The invention provides a voltage compensation driving circuit, which is used for dynamically adjusting compensation voltage according to output current of an output power supply so as to linearly control the brightness of a light-emitting element string.

The voltage compensation driving circuit of the invention is used for driving the light-emitting element string. The voltage compensation driving circuit comprises a power supply conversion circuit, a judging circuit, a processor, a boosting circuit and a boosting resistor. The power conversion circuit comprises a transformer, a primary side circuit for receiving an input power and a secondary side circuit coupled to the light emitting element string, wherein the transformer comprises a primary side winding coupled to the primary side circuit, a secondary side winding coupled to the secondary side circuit and an auxiliary winding. The transformer is used for converting an input power supply to generate an output power supply at a secondary side winding and generating an auxiliary power supply at an auxiliary winding. The judgment circuit is coupled to the auxiliary winding. The judging circuit is used for transmitting the auxiliary power supply according to the output current of the output power supply. The processor is coupled to the light emitting element string. The processor is used for adjusting the brightness of the light-emitting element string and providing a boosting control signal according to the output current. The boost control signal has a duty cycle corresponding to a current value of the output current. The boost circuit is coupled to the judgment circuit and the processor, and is used for boosting the auxiliary power supply according to the boost control signal to generate the compensation voltage. The boost resistor is coupled between the boost circuit and a high voltage end of the secondary side circuit, and is used for transmitting the compensation voltage to the light emitting element string.

In view of the above, the voltage compensation driving circuit of the present invention provides a boost control signal according to the output current, boosts the auxiliary power supply according to the boost control signal to generate a compensation voltage, and transmits the compensation voltage to the light emitting element string via the boost resistor. Therefore, the voltage compensation driving circuit can dynamically adjust the compensation voltage through the output current of the output power supply, and compensate the output voltage through the compensation voltage to linearly control the brightness of the light-emitting element string.

In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.

Drawings

Fig. 1 is a circuit diagram of a voltage compensation driving circuit according to a first embodiment of the invention.

Fig. 2 is a circuit diagram of a voltage compensation driving circuit according to a second embodiment of the invention.

[ description of symbols ]

100. 200: voltage compensation driving circuit

110. 210: power supply conversion circuit

120. 220, and (2) a step of: judging circuit

130. 230: processor with a memory having a plurality of memory cells

140. 240: voltage booster circuit

222: sensing circuit

224: comparator with a comparator circuit

226: buffer device

A Caux: auxiliary capacitor

Cb: boost capacitor

Co: output capacitor

And (3) Daux: auxiliary diode

Db: boost diode

Do: output diode

GND1, GND2: ground terminal

Io: output current

Lb: boost inductor

LD _1, LD _2, LD _3: light emitting element string

Naux: auxiliary winding

Np: primary side winding

Ns: secondary side winding

PI, PSB: output pin position

PS1, PS2: input pin position

Q1: main power switch

Qb: boost power switch

And Qd: auxiliary switch

Rm: boost resistor

Rq: resistance (RC)

Rs: sensing resistor

SB: boost control signal

SD: judging signal

SQ: switching signal

TR: transformer

VA: compensating voltage

Vaux: auxiliary power supply

Vin: input power supply

Vo: output power supply

VREF: reference voltage

Vs: sensing voltage

Detailed Description

Referring to fig. 1, fig. 1 is a circuit diagram of a voltage compensation driving circuit according to a first embodiment of the invention. In the present embodiment, the voltage compensation driving circuit 100 is used to drive the light emitting device strings LD _1, LD _2, and LD _3. The light emitting element strings LD _1, LD _2, and LD _3 are connected in parallel with each other. The light emitting element strings LD _1, LD _2, LD _3 may respectively have a single light emitting element or at least one light emitting element connected in series with each other. The Light-Emitting element may be, for example, a Light-Emitting Diode (LED), a Micro Light-Emitting Diode (Micro LED), or an Organic Light-Emitting Diode (OLED). For convenience of description, the number of the light emitting element strings in this embodiment is taken as 3 groups as an example, and the number of the light emitting element strings in the present invention may be one or more, and is not limited to this embodiment. The voltage compensation driving circuit 100 includes a power conversion circuit 110, a determination circuit 120, a processor 130, a boosting circuit 140, and a boosting resistor Rm.

The power conversion circuit 110 of the present embodiment includes a transformer TR, a primary side circuit, and a secondary side circuit. The transformer TR includes a primary winding Np coupled to the primary circuit, a secondary winding Ns coupled to the secondary circuit, and an auxiliary winding Naux. The transformer TR receives the input power Vin through a primary winding Np (i.e., a common-polarity terminal) and converts the input power Vin to generate the output power Vo at a secondary winding Ns and generate the auxiliary power Vaux at an auxiliary winding Naux. The primary side circuit of the present embodiment at least includes the main power switch Q1 and the resistor Rq, but the present invention is not limited thereto. A first terminal of the main power switch Q1 is coupled to the transformer TR. The control terminal of the main power switch Q1 is configured to receive the switching signal SQ to perform a switching operation of the main power switch Q1. The resistor Rq is coupled between the second terminal of the main power switch Q1 and the ground GND1 of the primary side circuit. The secondary side circuit of the present embodiment is coupled to the light emitting element strings LD _1, LD _2, and LD _3. The secondary-side circuit at least includes an output diode Do, an output capacitor Co, an auxiliary diode Daux, and an auxiliary capacitor Caux, but the invention is not limited thereto. An anode of the output diode Do is coupled to a first end (e.g., an alias end (not dotted)) of the secondary winding Ns. The cathode of the output diode Do is coupled to the first end of the output capacitor Co, and is used for outputting the output power Vo from the secondary winding Ns and serving as a high-voltage end of the secondary circuit. A first end of the output capacitor Co is coupled to a second end (e.g., the dotted end) of the secondary winding Ns and a ground GND2 of the secondary circuit. The anode of the auxiliary diode Daux is coupled to a first end of the auxiliary winding Naux (e.g., the alias end of the auxiliary winding Naux, i.e., unpunctured). The cathode of the auxiliary diode Daux is coupled to the determining circuit 120. The cathode of the auxiliary diode Daux is used to output the auxiliary power supply Vaux. The first terminal of the auxiliary capacitor Caux is coupled to the determining circuit 120. The second terminal of the auxiliary capacitor Caux is coupled to the second terminal of the auxiliary winding Naux (e.g., the dotted terminal of the auxiliary winding Naux).

In the present embodiment, the determination circuit 120 is coupled to the auxiliary winding Naux. The determining circuit 120 is configured to receive the output power Vo provided by the power converting circuit 110 and transmit the auxiliary power Vaux from the auxiliary winding Naux according to the output current Io of the output power Vo. The processor 130 is coupled to the light emitting device strings LD _1, LD _2, LD _3 and the determining circuit 120. The processor 130 is used for adjusting the brightness of the light emitting element strings LD _1, LD _2, and LD _3. For example, the processor 130 may perform linear current stabilization on the light emitting element strings LD _1, LD _2, and LD _3, respectively, or may equally distribute the output current Io to the light emitting element strings LD _1, LD _2, and LD _3. Besides, the processor 130 can provide the boost control signal SB according to the output current Io. The boost control signal SB has a duty cycle (duty cycle) corresponding to the output current Io. The boost circuit 140 is coupled to the determining circuit 120 and the processor 130. The boosting circuit 140 is used for boosting the auxiliary power supply Vaux according to the boosting control signal SB to generate the compensation voltage VA. That is, the boost circuit 140 generates the compensation voltage VA according to the auxiliary power source Vaux and the duty cycle. The voltage value of the compensation voltage VA is positively correlated with the duty cycle. The boost resistor Rm is coupled between the boost circuit 140 and the high voltage terminal of the secondary side circuit. The boosting resistor Rm is used for transmitting the compensation voltage VA to the light emitting device strings LD _1, LD _2, and LD _3, so as to drive the light emitting device strings LD _1, LD _2, and LD _3.

Specifically, the determination circuit 120 receives the output current Io and determines the voltage level of the determination signal SD according to the current value of the output current Io. When the determining circuit 120 determines that the current value of the output current Io is adjusted to be greater than a predetermined value, the determining signal SD with a high voltage level is provided. The determination circuit 120 transmits the auxiliary power source Vaux to the boost circuit 140 according to the determination signal SD of the high voltage level. On the other hand, when the judgment circuit 120 judges that the current value of the output current Io is adjusted to be less than or equal to the above-mentioned preset value, the judgment signal SD of a low voltage level is supplied. The determination circuit 120 does not transmit the auxiliary power Vaux according to the determination signal SD with the low voltage level. The judgment circuit 120 also supplies the judgment signal SD to the processor 130.

The processor 130 may receive the determination signal SD from the determination circuit 120. The processor 130 provides the boost control signal SB according to the voltage level of the determination signal SD. In this embodiment, the processor 130 may provide the boost control signal SB according to the high-voltage level determination signal SD, and not provide the boost control signal SB according to the low-voltage level determination signal SD. That is, when the current value of the output current Io is adjusted to be higher than the predetermined value, the determining circuit 120 transmits the auxiliary power source Vaux to the voltage boosting circuit 140, and the processor 130 also provides the voltage boosting control signal SB to drive the voltage boosting circuit 140. The voltage value of the compensation voltage VA is positively correlated with the duty cycle. The processor 130 also adjusts the duty cycle of the boost control signal SB according to the change of the current value of the output current Io. That is, the boost control signal SB has a duty cycle corresponding to the current value of the output current Io. Therefore, the boost circuit 140, upon receiving the boost control signal SB, boosts the auxiliary power supply Vaux according to the duty cycle of the boost control signal SB, so as to generate the compensation voltage VA. The boosting resistor Rm receives the compensation voltage VA generated by the boosting circuit 140 and transmits the compensation voltage VA to the high voltage terminal of the secondary circuit, so as to transmit the compensation voltage VA to the light emitting device strings LD _1, LD _2, LD _3.

On the other hand, when the current value of the output current Io is adjusted to be lower than the above-described preset value, the determination circuit 120 does not transmit the auxiliary power supply Vaux to the voltage boost circuit 140, and the processor 130 does not provide the boost control signal SB. Therefore, the boosting circuit 140 does not generate the compensation voltage VA, and the light emitting device strings LD _1, LD _2, and LD _3 are driven by the output power Vo generated by the secondary winding Ns.

It should be noted that the voltage compensation driving circuit 100 provides a boost control signal SB according to the output current Io, boosts the auxiliary power source Vaux according to the boost control signal SB to generate a compensation voltage VA, and transmits the compensation voltage VA to the light emitting device strings LD _1, LD _2, and LD _3 through the boost resistor Rm. As such, the voltage compensation driving circuit 100 can dynamically adjust the compensation voltage VA by the output current Io of the output power Vo, and compensate the output voltage Vo by the compensation voltage VA to linearly control the brightness of the light emitting device strings LD _1, LD _2, LD _3.

Referring to fig. 2, fig. 2 is a circuit diagram of a voltage compensation driving circuit according to a second embodiment of the invention. In the present embodiment, the voltage compensation driving circuit 200 includes a power conversion circuit 210, a determination circuit 220, a processor 230, a voltage boosting circuit 240, and a voltage boosting resistor Rm. The coupling relationship among the power conversion circuit 210, the determination circuit 220, the processor 230, the voltage boost circuit 240 and the voltage boost resistor Rm can be taught sufficiently in the first embodiment, and therefore, will not be repeated here. In the present embodiment, the determining circuit 220 includes a sensing circuit 222, a comparator 224 and an auxiliary switch Qd. Implementation details of the power conversion circuit 210 may be sufficiently taught by the power conversion circuit 110 of the first embodiment, and therefore, are not repeated here. The sensing circuit 222 is configured to receive the output current Io of the output power Vo through the light emitting device strings LD _1, LD _2, LD _3 and the processor 230, and generate the sensing voltage Vs according to the output current Io. The sensing circuit 222 may include at least a sensing resistor Rs. The first terminal of the sense resistor Rs is coupled to the processor 230 for receiving the output current Io. The second end of the sensing resistor Rs is coupled to the ground GND2 of the secondary side circuit.

It should be noted that the resistance value of the boosting resistor Rm is designed to be significantly higher than that of the sensing resistor Rs. The resistance value of the boosting resistor Rm is designed to be more than 10 times the resistance value of the sensing resistor Rs. For example, the resistance of the boost resistor Rm is 10 mega ohms (M Ω), and the resistance of the sense resistor Rs is 1 ohm. Such a design can ensure that the output power Vo can efficiently drive the light emitting element strings LD _1, LD _2, LD _3 without causing the output power Vo to enter the voltage boosting circuit 240 via the voltage boosting resistor Rm.

The non-inverting input of the comparator 224 is coupled to the sensing circuit 222. The inverting input of the comparator 224 receives the reference voltage VREF. The comparator 224 provides the determination signal SD via the output terminal of the comparator 224 according to the comparison result between the sensing voltage Vs and the reference voltage VREF.

A first terminal of the auxiliary switch Qd is coupled to a first terminal of the auxiliary winding Naux. I.e. the first terminal of the auxiliary switch Qd is able to receive the auxiliary power supply Vaux via the auxiliary diode Daux. The second terminal of the auxiliary switch Qd is coupled to the boost circuit 240, and the control terminal of the auxiliary switch Qd is coupled to the output terminal of the comparator 224. The control terminal of the auxiliary switch Qd may be turned on or off according to the voltage level of the sensing voltage Vs.

In some embodiments, the decision circuit 220 may further include a buffer 226. The buffer 226 is coupled between the output terminal of the comparator 224 and the control terminal of the auxiliary switch Qd. The buffer 226 may provide a switching signal to the control terminal of the auxiliary switch Qd according to the voltage level of the determination signal SD. In some embodiments, the buffer 226 may gain the voltage value of the determination signal SD to provide the switching signal. The voltage level of the switching signal is greater than the high voltage level of the determination signal SD. In this way, the buffer 226 can further ensure that the auxiliary switch Qd can be completely turned on or off under the driving of the switching signal.

Processor 230 includes output pins PI, PSB and input pins PS1, PS2. The processor 230 may provide an output current Io to the sensing circuit 222 via the output pin PI. The processor 230 can receive the sensing voltage Vs via the input pin PS1 to know the variation of the output current Io. In the present embodiment, the processor 230 can know the current value change of the output current Io according to the sensing voltage Vs and the resistance inside the processor 230. The processor 230 receives the determination signal SD via the input pin PS2 and provides the boost control signal SB via the output pin PSB according to the voltage level of the determination signal SD.

The boost circuit 240 includes a boost inductor Lb, a boost diode Db, a boost capacitor Cb, and a boost power switch Qb. The first terminal of the boost inductor Lb is coupled to the determining circuit 220 for receiving the auxiliary power source Vaux. The first end of the boost inductor Lb is coupled to the auxiliary switch Qd to receive the auxiliary power source Vaux via the turned-on auxiliary switch Qd. The anode of the boost diode Db is coupled to the second end of the boost inductor Lb. The first end of the boost capacitor Cb is coupled to the cathode of the boost diode Db. The second terminal of the boost capacitor Cb is coupled to the auxiliary winding Naux, i.e., the second terminal of the auxiliary winding Naux. The first terminal of the boost power switch Qb is coupled to the second terminal of the boost inductor Lb. The second terminal of the boost power switch Qb is coupled to the second terminal of the boost capacitor Cb. The control terminal of the boost power switch Qb is coupled to the processor 230 to receive the boost control signal SB. The switching frequency of the boost power switch Qb and the switching frequency of the main power switch Q1 may be the same, i.e., the frequency of the switching signal SQ and the frequency of the boost control signal SB are the same. In some embodiments, the switching frequency of the boost power switch Qb and the switching frequency of the main power switch Q1 may not be the same, i.e., the frequency of the switching signal SQ and the frequency of the boost control signal SB may not be the same.

For example, the voltage value of the reference voltage VREF may be set to 1.9 volts. The resistance value of the sense resistor Rs may be set to 1 ohm. When the luminances of the light emitting element strings LD _1, LD _2, and LD _3 are low, the current value of the output current Io is 1.5 amperes. The sensing circuit 222 receives the output current Io and generates a sensing voltage Vs accordingly. The sensing voltage Vs is 1.5 volts at this time. The comparator 224 determines that the voltage level of the sensing voltage Vs (1.5 volts) is lower than the voltage level of the reference voltage VREF (1.9 volts). Therefore, the comparator 224 provides the determination signal SD with a low logic level. The auxiliary switch Qd is turned off according to the determination signal SD of low logic level. Therefore, the auxiliary power supply Vaux is not transmitted to the voltage boosting circuit 240. In addition, the processor 230 does not provide the boost control signal SB according to the determination signal SD of low logic level. Therefore, the boost circuit 240 does not operate.

For another example, when the brightness of the light emitting element strings LD _1, LD _2, LD _3 is increased to increase the current value of the output current Io to 2 amperes, the sensing circuit 222 receives the output current Io and generates the sensing voltage Vs accordingly. The sensing voltage Vs is 2 volts at this time. The comparator 224 determines that the voltage level of the sensing voltage Vs (2 volts) is higher than the voltage level of the reference voltage VREF (1.9 volts). Therefore, the comparator 224 provides the high logic level of the determination signal SD. The auxiliary switch Qd is turned on according to the determination signal SD of high logic level. Therefore, the auxiliary power supply Vaux can be transmitted to the voltage boosting circuit 240. In addition, the processor 230 provides the boost control signal SB according to the determination signal SD with a high logic level, and adjusts the duty cycle of the boost control signal SB according to the variation of the output current Io. If the processor 230 determines that the output current Io is continuously adjusted high, the processor 230 increases the duty cycle of the boost control signal SB. The boosting circuit 240 increases the voltage value of the compensation voltage VA according to the duty cycle of the boosting control signal SB. If the processor 230 determines that the output current Io is adjusted to be low, the processor 230 decreases the duty cycle of the boost control signal SB. The boosting circuit 240 decreases the voltage value of the compensation voltage VA according to the duty cycle of the boosting control signal SB. In the present embodiment, the duty cycle may be adjusted to 0.3 to 0.8, but the present invention is not limited thereto.

It should be noted that the voltage compensation driving circuit 200 can dynamically adjust the compensation voltage VA according to the variation of the output current Io, so that the voltage compensation driving circuit 200 does not decrease the voltage value due to the increase of the output current Io. In this way, the voltage compensation driving circuit 200 linearly controls the brightness of the light emitting device strings LD _1, LD _2, and LD _3.

In summary, the voltage compensation driving circuit of the present invention can provide the boost control signal according to the variation of the output current, boost the auxiliary power source according to the boost control signal to generate the compensation voltage, and transmit the compensation voltage to the light emitting device string through the boost resistor. Therefore, the voltage compensation driving circuit can dynamically adjust the compensation voltage according to the output current, and the output voltage is compensated through the compensation voltage to linearly control the brightness of the light-emitting element string. Thus, linear control of the luminance of the light emitting element string by adjustment of the output current is realized.

Although the present invention has been described with reference to the above embodiments, it should be understood that various changes and modifications can be made therein by those skilled in the art without departing from the spirit and scope of the invention.

Claims

1. A voltage compensation driving circuit for driving at least one light emitting device string, the voltage compensation driving circuit comprising:

a power conversion circuit having a transformer, a primary side circuit for receiving an input power, and a secondary side circuit coupled to the at least one light emitting device string, wherein the transformer includes a primary side winding coupled to the primary side circuit, a secondary side winding coupled to the secondary side circuit, and an auxiliary winding, wherein the transformer is configured to convert the input power to generate an output power at the secondary side winding and an auxiliary power at the auxiliary winding;

the judging circuit is coupled to the auxiliary winding and used for transmitting the auxiliary power supply according to the output current of the output power supply;

a processor, coupled to the at least one light emitting element string, for adjusting a brightness of the at least one light emitting element string and adjusting a duty cycle of a boost control signal according to a change in a current value of the output current, wherein the duty cycle corresponds to a current value of the output current;

a boost circuit, coupled to the determination circuit and the processor, for boosting the auxiliary power according to the boost control signal to generate a compensation voltage, wherein a voltage value of the compensation voltage is positively correlated to the duty cycle; and

and the boosting resistor is coupled between the boosting circuit and the high-voltage end of the secondary side circuit and used for transmitting the compensation voltage to the at least one light-emitting element string.

2. The voltage compensation driving circuit according to claim 1, wherein the judging circuit includes:

a sensing circuit for receiving the output current via the at least one light emitting element string and the processor and generating a sensing voltage according to the output current;

a comparator, a non-inverting input terminal of which is coupled to the sensing circuit, an inverting input terminal of which is configured to receive a reference voltage, wherein the comparator provides a determination signal via an output terminal of the comparator according to a comparison result between the sensing voltage and the reference voltage; and

a first terminal of the auxiliary switch is coupled to the first terminal of the auxiliary winding, a second terminal of the auxiliary switch is coupled to the boost circuit, and a control terminal of the auxiliary switch is coupled to the output terminal of the comparator.

3. The voltage compensation driving circuit of claim 2, wherein the determining circuit turns on the auxiliary switch when the voltage value of the sensing voltage is greater than the voltage value of the reference voltage, thereby providing the auxiliary power to the boosting circuit.

4. The voltage compensation driving circuit of claim 2, wherein the processor is further configured to receive the determination signal, provide the boost control signal according to a voltage level of the determination signal, and adjust the duty cycle of the boost control signal according to a change of the output current.

5. The voltage compensation driving circuit of claim 4, wherein the processor provides the boost control signal when the voltage level of the determination signal is a high voltage level, and the processor increases the duty cycle of the boost control signal in accordance with the increased output current.

6. The voltage compensation driving circuit of claim 2, wherein the sensing circuit comprises:

a first end of the sensing resistor is coupled to the processor to receive the output current, and a second end of the sensing resistor is coupled to a ground end of the secondary side circuit.

7. The voltage compensation driving circuit of claim 6, wherein a resistance value of the boost resistor is greater than a resistance value of the sense resistor.

8. The voltage compensation driving circuit according to claim 2, wherein the determining circuit further comprises:

and the buffer is coupled between the output end of the comparator and the control end of the auxiliary switch and used for providing a switching signal to the control end of the auxiliary switch according to the voltage level of the judgment signal.

9. The voltage compensation driver circuit of claim 1, wherein the boost circuit comprises:

a boost inductor, a first end of the boost inductor being coupled to the determination circuit to receive the auxiliary power;

a boost diode, an anode of the boost diode being coupled to a second end of the boost inductor;

a boost capacitor, a first end of the boost capacitor being coupled to a cathode of the boost diode, a second end of the boost capacitor being coupled to the auxiliary winding; and

a boost power switch, a first terminal of the boost power switch coupled to the second terminal of the boost inductor, a second terminal of the boost power switch coupled to the second terminal of the boost capacitor, and a control terminal of the boost power switch coupled to the processor for receiving the boost control signal.