KR910000019Y1 - Rear-view mirror - Google Patents

Abstract

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Description

Reflectivity automatic adjustment liquid crystal rearview driving circuit

1 is a block diagram of a conventional liquid crystal rearview driving circuit.

2 is a circuit diagram of the present invention.

3 is a partial operation waveform diagram of FIG.

* Explanation of symbols for main parts of the drawings

10: optical sensing switching unit 20: optical signal logic output unit

30: decoder 40: oscillator

50: drive voltage generator

The present invention relates to a liquid crystal rearview driving circuit, and more particularly, to a liquid crystal rearview driving circuit for automatically adjusting the reflectance of a liquid crystal rearview mirror.

In the conventional liquid crystal rearview driving circuit, as illustrated in FIG. 1, a light quantity sensing unit 1 for sensing a light quantity of a headlight of a rear vehicle and outputting a light sensing voltage, and a light sensing unit of the light quantity sensing unit 1 The light quantity comparing unit 2 outputs a predetermined light quantity comparing voltage when the light sensing voltage is large by comparing the voltage with a reference voltage of a predetermined level, and a signal having a predetermined period when the light quantity comparing voltage is output from the light quantity comparing unit 2. Oscillation unit 3 for oscillating output, a liquid crystal driver 4 for outputting a liquid crystal driving voltage having a phase opposite to the oscillation output, and a headlight of a rear vehicle driven by the output liquid crystal driving voltage It consists of the liquid crystal back-view mirror 5 which lowers to a value and reflects only a predetermined amount.

In the circuit configured as described above, when the light sensor of the light quantity detecting unit 1 converts and outputs the intensity of the external light amount of the headlight of the vehicle coming from the rear, the light quantity comparing unit 2 is preset to a predetermined level. When the electrical signal of the light sensing is large compared to the voltage, the light sensing comparison voltage is input to the oscillator 3 at a voltage of the "high" potential.

At this time, the oscillator 3 which inputs the light quantity comparison voltage "high" oscillates a square wave signal of a predetermined period and outputs it to the liquid crystal driver 4 so that the liquid crystal drive frequency of the AC state in which the phases are opposite to each other in the liquid crystal driver 4 is measured. Output to the endoscope (5).

Therefore, the liquid crystal rearview mirror 5, which inputs the liquid crystal driving frequency output from the liquid crystal driving unit 4, attenuates and reflects the headlight light emitted from the rear vehicle to a predetermined value or less to prevent the glare of the driver.

However, in the conventional liquid crystal rearview driving circuit operated as described above, when the output of the light quantity comparing unit 2 is "low", the liquid crystal rearview 5 is "off" and reflects the incident light at 100%. When the output is "high", the liquid crystal rearview mirror 5 is turned "on" to lower the reflectance of the headlight light to a constant value to prevent glare, so that the liquid crystal rearview mirror 5 at the threshold value of the external light in which the light quantity comparison unit 2 is operated. ) Is not driven so that the reflectance is high when the "off" state, the glare may occur, the problem is that it is too dark at the "on" time.

That is, according to the amount of light, the liquid crystal rearview mirror 5 was simply driven in two stages of on / off, and thus the reflectance of the headlight light could not be adjusted.

Accordingly, an object of the present invention is to provide a driving circuit of the liquid crystal rearview mirror that can adjust the reflectance of the liquid crystal rearview mirror according to the intensity of the headlight light amount of the rear vehicle.

Another object of the present invention is to provide a circuit for converting and processing a photoelectric conversion signal of the headlight light intensity of the rear vehicle by comparing a photoelectric conversion signal with a logic signal capable of adjusting the reflectance.

Another object of the present invention is to provide a circuit capable of converting the duty of the liquid crystal rearview driving frequency according to the intensity of the photoelectric conversion signal.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 is a circuit diagram according to the present invention, which is composed of a resistor (R1-R4), a photodiode (PD) and a transistor (Q1-Q2), the power supply voltage (Vcc) by switching the power supply voltage (Vcc) when the amount of received light is constant or more And an optical sensing switch 10 for outputting an optical sensing voltage VP1 and a resistor R6-R10 and a comparator OP1-OP2, and the voltage Vcc in the optical sensing switching unit 10. The voltage Vcc is divided at the switching output to generate a reference voltage VP2-VP3 having a different level, and the generated reference voltage VP2-VP3 and the light sensing voltage VP1 of the light sensing switching unit 10 are generated. ) Is composed of an optical signal logic converter 20 for outputting first and second comparison logic signals with respect to the amount of light sensing voltage, and gates G1-G2, respectively. The decoder unit 30 outputs the first and second oscillation control signals by decoding the output signal of the signal, and the resistors R11 to R18 and the capacitor C1 are non- An oscillator 40 configured to oscillate and output a frequency by varying an oscillation duty in accordance with the first and second oscillation control signals of the decoder unit 30, and a D-type latch DF1. A demultiplexer (DMUX) and a buffer (BUF1-BUF2) are configured to convert the output of the oscillator 40 into a signal of a predetermined period to demultiplex the oscillation frequency to drive a drive signal for driving the liquid crystal rearview mirror 60. It consists of the drive voltage generation part 50 which outputs.

In the structure of FIG. 2, the resistors R6-R8 connected in series between the power supply voltage line VccL and the ground in the optical signal logic converter 20 are connected to the power supply voltage line through the collector of the transistor Q1. A reference voltage generator circuit generates a reference voltages VP2 and VP3 having different levels by resistance-dividing the power supply voltage Vcc input to VccL).

A D type latch (D type flip-flop) in the driving voltage generator 50 divides the clock pulse input to the clock terminal CK into a select control signal of a D multiplexer (DMUX). Output

The demultiplexer DMVX multiplexes the signal input from the terminal C according to the output logic of the D-type latch DF1 and outputs the signal to the output terminal a or the terminal b.

Reference numerals UE and LE are upper and lower transparent electrodes of the liquid crystal rearview mirror 60, and the liquid crystal rearview mirror 60 is driven by an effective value of an AC voltage applied to both the UE and LE terminals.

3 is an operation waveform diagram of a part of FIG. 2, (a) is an oscillation waveform, which is an output of the comparator OP3 of the oscillator 40, and (b) is an oscillation frequency divided by the D-type latch DF1 and output. (C) and (d) are the output waveforms output from the output terminals (a) and (b) of the demultiplexer (DMUX) when demultiplexing the waveform of a through the selection control signal. , e is a waveform diagram of the input voltage between the UE and the LE electrode of the liquid crystal endoscope 60.

In the t1 section of the waveform of FIG. 3, the photosensing PD detects the rear vehicle and thus the optical sensing voltage VP1, which appears between both terminals of the resistor R5, is less than the reference voltage VP3 in the optical signal logic output unit 20. It is the operating waveform when it is larger and less than the reference voltage VP2 (VP3 <VP1 <VP2), and the t2 section is when the light sensing voltage VP1 is larger than the reference voltage VP2 and VP3 (VP3 <VP2 <VP1). The operating waveform of.

Hereinafter, an embodiment of the present invention will be described with reference to the configuration of FIG. 2 and the waveform diagram of FIG. 3.

The light of the headlight followed by the photodiode PD from the rear with the power supply voltage Vcc being input to the emitter of the transistor Q1 through the cathode and the resistor R1 of the photodiode PD. Assuming that is detected and converted to an electrical signal, the electrical conversion signal of the photodiode PD causes a voltage drop to the resistor R5.

Therefore, the light sensing voltage VP1 that is displayed across the resistor R5 is converted according to the intensity of the headlight of the vehicle following from the rear.

If the received light is weak, i.e., less than the reference light amount, the electrical change in the amount of light received by the photodiode PD is small so that the light sensing voltage VP1, which is the voltage across the resistor R5, is small.

When the light sensing voltage VP1 by the photodiode PD and the resistor R5 is input to the base with a voltage that cannot saturate the transistor Q2, the transistor Q1 is in the cut off region. By operation, the transistor Q is not " turned on " so that the power supply voltage Vcc is not input to each circuit.

On the other hand, when the light of the headlight of the rear vehicle is strong and the photodiode PD, which receives the light and outputs it as an electric signal, is greatly saturated, the light sensing voltage VP1, which is the voltage at both ends of the resistor R5, becomes large so that the resistor R3 and R4 When the voltage divided by the voltage rises and the voltage reaches the saturation current of the transistor Q2, the transistor Q2 operates in the saturation region to receive the voltage input to the collector through the resistors R1-R2. Bypass between collector and emitter to ground.

Transistor Q1 is thus " turned on " to supply power supply voltage Vcc to the operating power supply of each circuit via power supply voltage line VccL.

In this case, the comparators OP1 to OP2 input the photo voltage VP1 sensed by the photodiode PD to the non-inverting terminal (+) by the input of the power supply voltage Vcc.

The comparators OP1-OP2 inputting the optical sensing voltage VP1 are respectively inputted with reference voltages VP2 and VP3, which are divided voltages of the resistors R6-R8 connected in series, to the inverting terminal (−).

In this case, the voltage magnitudes of the reference voltage VP2 input to the comparator OP1 and the divided voltage VP3 input to the comparator OP2 are as follows.

As can be seen from the above equations (1) and (2), the magnitude relationship between the reference voltage VP2 and VP3 becomes VP2> VP3 so that the light sensing voltage VP1 becomes the reference voltage VP3 of the comparator OP2. When smaller than VP1 < VP3 < VP2, the outputs of the first and second comparative logic signals outputting the relationship between the optical sensing voltage VP1 and the reference voltage VP2 and VP3 are respectively output from the comparators OP1 to OP2. Prints "

Therefore, the gates G1-G2 output the first and second oscillation control signals of the respective logic " low ", which causes the comparator OP3 to continuously output the logic of the “high” state.

As described above, when the comparator OP3 continuously outputs a "high" state, the logic of the clock terminal CK is output to the output terminal Q because the logic of the clock terminal CK does not change in the D-type latch DF1. Since it is not changed, the output terminal Q outputs the state of "high" or "low" previously output (Lstching).

Accordingly, since the demultiplexer DMUX does not perform the multiplexing operation, the signal input to the terminal C is continuously output to one terminal of the terminal b or the terminal a. Therefore, since the AC driving voltage is not applied at both ends of the UE and the LE of the liquid crystal rearview mirror 60, the liquid crystal rearview mirror 60 is not driven and reflects incident light at 100%.

When the headlight of the rear vehicle becomes stronger in the above operation state, the light sensing voltage VP1 of the photodiode PD is increased, and the increased light sensing voltage VP1 is the inverting end of the comparator OP2. When the voltage becomes greater than the reference voltage VP3 inputted as-) and becomes VP2> VP1> VP3, the comparators OP1-OP2 respectively resist the first comparison logic signal of "low" and the second comparison logic signal of "high", respectively. Outputs to both input terminals of the gates (G1) and (G2) through (R10) and (R9).

Here, resistors R10 and R9 are resistors that pull up logic "high" outputs of comparators OP1 and OP2. Therefore, the outputs of the comparators OP1 and OP2 are Only the gate G2 among the gates G1 and G2 respectively input to each other charges the second oscillation suppressor signal of logic " high &quot; through the resistor R12 to the capacitor C1 with time constants of R12 and C1. This charging potential is input to the inverting terminal (-) of the comparator OP3.

At this time, the voltage due to the RC charging time constant of the resistor R12 and the capacitor C1 increases to divide the voltage input to the non-inverting terminal (+) of the comparator OP3, that is, the resistors R14-R16 to divide the resistance ( When the voltage is greater than the voltage input through R17), the comparator OP3 outputs a signal based on the RC time constant as shown in (a) of FIG.

Therefore, the DD-type latch DF1 inputs the output of FIG. 3a to the clock terminal CK, divides the signal input to the clock terminal CK into 2 as shown in FIG. 3b, and supplies the oscillation output of the comparator OP3 to the terminal ( Outputs the selection control signal of the demultiplexer (DMUX) input to C).

On the other hand, the demultiplexer DMUX inputting the oscillation output of the comparator OP3 to the terminal C and the output of the D-type latch DF1 as a control signal oscillates at the time t1 in FIG. 3 (a) of FIG. 3a) When the output of the D-type latch DF1 is "high" as shown in FIG. 3b, the signal is output to the terminal a as shown in FIG. 3c, which is transparent through the buffer BUF1. It is input to the electrode UE. When the output of the D-type latch DF1 is "low", the demultiplexer DMUX outputs the signal (2a) (4a) of FIG. 3a input to the terminal C to the terminal b as shown in FIG. 3d. This is input to the lower transparent electrode LE of the liquid crystal display mirror 60 through the buffer BUF2.

Accordingly, the demultiplexer DMUX oscillates from the oscillator 40 as shown in 1a, 2a, 3a, 4a of FIG. 3a, and inputs the signal input to the terminal C by the output of the D-type latch DF1. As shown in Fig. 2, the output terminals b and C are multiplexed and input to the buffers BUF1 and BUF2.

In this case, the buffers BUF1 and BUF2 buffer respective inputs and output the buffers to the liquid crystal rearview mirror 60 so that the liquid crystal rearview mirror 60 is driven by the liquid crystal driving voltage as shown in FIG. It scatters in proportion to the liquid crystal driving voltage.

As described above, the headlight light of the rear vehicle is strongly detected by the photodiode PD during driving, and thus the light sensing voltage VP1 is increased from the previous state so that the reference voltages VP2 and VP3 by the resistors R6-R8 are increased. If the magnitude relationship is greater than VP3 < VP2 < VP1, the comparators OP1-OP2 both transmit the first and second comparison logic signals in the " high " state by the resistors R9-R10 to the gate G1 and ( Output to both terminals of G2). As a result, only the gate G1 of the gates G1 and G2 charges the "high" signal to the first oscillation control signal to charge the capacitor C1 through the resistors R11-R12.

Therefore, the oscillation period of the comparator OP3 is oscillated by the RC time constant of (R11 + R12) C1 by the resistors R11-R12 and the capacitor C1, so that the oscillation period is dutyier than the period T1 at time t1 in FIG. An oscillation signal having a large duty is oscillated and output at a period T2 at the time t2 at which the light sensing voltage VP1 of the photodiode PD increases.

At time t2 of FIG. 3, the oscillation signal is multiplexed into a waveform having a period t1 at time t2 as shown in FIG. 3c, d by the D-type latch DF1 and the multiplexer DMUX along the path as described above. The upper and lower transparent electrodes UE LE of the liquid crystal display mirror 60 are respectively input.

At this time, the signals output from the terminals (a) and (C) of the demultiplexer (DMUX) as shown in (c) and (d) of time t2 in FIG. 3 are respectively passed through the buffers BUF1 and BUF2. ), The effective voltage across the upper and lower transparent electrodes UE and LE of the liquid crystal display mirror 60 increases as shown in (e) of FIG.

Accordingly, the liquid crystal rearview mirror 60 further scatters the light incident by the signal at time t2 of FIG. 3 at which the duty is greater than that of the liquid crystal driving voltage at time t1 of FIG.

As described above, the present invention changes the duty ratio of the liquid crystal rearview driving frequency according to the magnitude of the light quantity sensing voltage of the rear vehicle, thereby increasing the effective voltage between the liquid crystal rearview mirrors, thereby controlling the reflectance, thereby improving the product quality. There is a measurable advantage.

Claims (2)

A reflectance automatic adjustment liquid crystal rearview driving circuit including a liquid crystal rearview mirror 60 having upper and lower transparent electrodes (UE) (LE), wherein the power supply voltage when the amount of received light of the headlight light emitted from the rear vehicle is a predetermined amount or more. A light sensing switching unit 10 for switching the Vcc to supply a power supply voltage Vcc and converting it into an electrical signal and outputting a light sensing voltage VP1 and a voltage of the light sensing switching unit 10. It is connected to the output terminal and the light sensing output terminal and divides the switching input voltage Vcc to divide the resistance voltage of the reference voltages VP1-VP2 having different levels, and at the same time, the light inputted with the reference voltages VP2 and VP3. An optical signal logic converter 20 for comparing the sensing voltage VP1 and outputting first and second comparison logic signals with respect to the magnitude of the light quantity sensing voltage, and a terminal of the optical signal logic converter 20 The first and second comparison logic signals A decoder unit 30 which decodes and outputs first and second oscillation control signals, and is connected to an output terminal of the decoder unit 30 and oscillates and outputs a frequency in response to an input second oscillation control signal. An oscillation unit 40 for oscillating and outputting the oscillation frequency by varying the duty of the oscillation frequency by input of an oscillation control signal, and divides the oscillation signal that is input and divided into 2 The driving signal outputs a driving signal for driving the liquid crystal rearview mirror 60 by demultiplexing the oscillation frequency into the upper transparent electrode UE and the lower transparent electrode LE of the liquid crystal rearview mirror 60 as a divided signal. Reflectance automatic adjustment liquid crystal rearview driving circuit characterized by comprising a voltage generator (50). The D-type latch DF1 of claim 1, wherein the driving voltage generator 50 inputs the oscillation signal of the oscillator 40 to the clock terminal CK, and outputs two divided outputs. Demultiplexer (DMUX) for demultiplexing and outputting the oscillation signal of the oscillator 40 to two output terminals under the control of the signal divided by two divided outputs, two output terminals of the demultiplexer (DMUX) and the liquid crystal rear A buffer BUF1 and BUF2 connected between the upper and lower transparent electrodes UE LE of the endoscope 60 to buffer the output of the demultiplexer DMUX and output the buffer to the liquid crystal rearview mirror 60. Reflective automatic adjustment liquid crystal rearview driving circuit characterized in that.