KR100931408B1 - Power folding mirror and operating circuits for the same - Google Patents

Abstract

PURPOSE: A power folding mirror and a driver circuit thereof are provided to protect a motor by turning off a switching device with a second transistor, which drops a bias voltage to a turn-off level, when detected voltage is over a cut-off voltage. CONSTITUTION: A switching device(40) is turned on/off by bias voltage. A motor(50) is turned on by turning on the switching device. A current detector(60) outputs detection voltage by detecting current flowing in the motor. A fold-back unit(70) includes a first transistor(T1,T2) and a second transistor(T3,T4). The first transistor includes a first control receiving the detection voltage. The second transistor includes a second control terminal connected to a first terminal of the first transistor. If the detection voltage is over the cut-off voltage, the second transistor turns off the switching device by dropping the bias voltage to a turn-off level.

Description

Power Folding Mirror and Operating Circuits

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power folding mirror and a driving circuit thereof, and more particularly, to a power folding mirror and a driving circuit thereof that can prevent burnout of a motor and operate reliably.

In general, vehicle side mirrors are provided at predetermined portions of the left and right sides of the vehicle body, respectively. The driver may adjust the side mirrors at a predetermined angle to grasp the situation of the rear and left and right sides of the vehicle when the vehicle is driven.

However, there are times when the side mirror becomes an obstacle, such as when parking on a narrow street. In this case, when the side mirror becomes an obstacle, a power folding mirror has been developed that allows the driver to operate the switch in the driver's seat to fold the side mirror and re-open it during driving.

As a circuit for driving a power folding mirror, a circuit using a PTC (Positive Temperature Coefficient) element and a fold-back circuit using a resistor have been proposed. Here, the PTC element is an element whose resistance value increases as the temperature rises.

In the process of operating the motor to fold or unfold the power folding mirror, if the power folding mirror rotates to the stop position, the gears stop and the power folding mirror can no longer be rotated. The current continues to flow in the motor, but because the motor is forcibly stopped, the motor is overloaded and an overcurrent flows. This is called a stall current.

In a circuit using the PTC element, the PTC element has a high temperature due to heat generated by the stall current, and the impedance value is increased to block the flow of current. In other words, the circuit is cut off using the switch characteristic of the PTC element. On the other hand, in a fold-back circuit using a resistor to detect the stall current flowing through the resistor to cut off the circuit.

SUMMARY OF THE INVENTION An object of the present invention is to provide a power folding mirror driving circuit that prevents burnout of a motor and operates reliably.

Accordingly, an object of the present invention is to provide a power folding mirror that prevents burnout of a motor and operates reliably.

Problems to be solved by the present invention are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

The power folding mirror driving circuit according to an embodiment of the present invention for solving the above problems, the switching element is turned on / off by the bias voltage, the motor is driven by the switching element is turned on, and the current flowing through the motor A current transistor configured to sense and output a sensed voltage, a first transistor having a first control terminal to which a sense voltage is applied, and a second transistor having a second control terminal coupled to one terminal of the first transistor; And fold-back. The second transistor turns the switching device off by stepping down the bias voltage to the turn-off level when the sense voltage is greater than or equal to the blocking voltage.

The power folding mirror according to an embodiment of the present invention for achieving the another object, the switching element is turned on / off by the bias voltage, the motor is driven by the switching element is turned on, and the current flowing through the motor And a current transistor configured to output a sense voltage, a first transistor having a first control terminal to which the sense voltage is applied, and a second transistor having a second control terminal coupled to one terminal of the first transistor. A power folding mirror drive circuit comprising a fold-back portion, a motion transmission portion for transmitting a rotational movement of the relay driven motor, and a mirror rotated by the motion transmission portion. The second transistor turns the switching device off by stepping down the bias voltage to the turn-off level when the sense voltage is greater than or equal to the blocking voltage.

Other specific details of the invention are included in the detailed description and drawings.

According to the power folding mirror and the driving circuit thereof according to the present invention, the following effects are obtained.

First, since the switching speed is short, the burnout of the motor due to the stall current can be prevented. In other words, even if a stall current occurs in the motor, the circuit is cut off within a short time, thereby protecting the motor.

Second, even if the driver operates the switch again while the driver operates the switch to fold or unfold the power folding mirror, the power folding mirror driving circuit may operate normally.

Third, even when positive transient noise or negative transient noise is introduced from the outside in a situation where the motor is forcibly stopped, the power folding mirror driving circuit may operate normally.

Fourth, even if the magnitude of the voltage applied to the foldback part when the motor is stopped varies depending on the temperature change, the possibility of motor burnout by the stall current can be reduced by stably shutting off the power supply to the motor.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but may be embodied in various different forms, and the present embodiments merely make the disclosure of the present invention complete, and are common in the art to which the present invention pertains. It is provided to fully inform those skilled in the art of the scope of the invention, which is to be defined only by the scope of the claims.

When one element is referred to as being "connected to" or "coupled to" with another element, when directly connected to or coupled with another element, or through another element in between Include all cases. On the other hand, when one device is referred to as "directly connected to" or "directly coupled to" with another device indicates that no other device is intervened.

Although the first, second, etc. are used to describe various elements, components and / or sections, these elements, components and / or sections are of course not limited by these terms. These terms are only used to distinguish one element, component or section from another element, component or section. Therefore, the first element, the first component or the first section mentioned below may be a second element, a second component or a second section within the technical spirit of the present invention.

Like reference numerals refer to like elements throughout. “And / or” includes each and all combinations of one or more of the items mentioned. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” and / or “comprising” refers to the presence of one or more other components, steps, operations and / or elements. Or does not exclude additions.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used in a sense that can be commonly understood by those skilled in the art. In addition, the terms defined in the commonly used dictionaries are not ideally or excessively interpreted unless they are specifically defined clearly.

1 is a perspective view schematically showing the structure of a power folding mirror according to an embodiment of the present invention.

Referring to FIG. 1, a power folding mirror according to an embodiment of the present invention may include a mirror 9, a power folding mirror driving circuit including a motor M (see 1 in FIG. 2), a door bracket 7, and a door. Hinge 2, and movement transmissions 3, 5. The motion transmission part 3, 5 here comprises a first gear 5 and a second gear 3.

The motor M is installed in the interior space of the mirror 9, and the 1st gear 5 is axially installed in the shaft end. The mirror bracket 2 is attached to the door bracket 7, and the second gear 3 is shaft-mounted at the shaft end thereof. Here, the first gear 5 and the second gear 3 are provided to mesh with each other.

When the motor M is rotated forward or reversely by the power folding mirror driving circuit, the mirror 9 is forward or reversed through the first gear 5 and the second gear 3 engaged with each other. It works. In other words, the mirror 9 performs the forward (folding) operation or the reverse (unfolding) operation with the mirror hinge 2 as the central axis. Then, when the mirror 9 rotates to the stop positions P1 and P2 by performing the forward operation or the reverse operation, the gears are stopped so that the mirror 9 can no longer be rotated and the motor M is forcibly stopped.

2 is a circuit diagram illustrating a power folding mirror driving circuit according to an exemplary embodiment of the present invention.

Referring to FIG. 2, the power folding mirror driving circuit 1 according to an embodiment of the present invention includes a power supply unit 10, an abnormal signal blocking unit 20, a bias voltage providing unit 30, a switching unit 40, The motor unit 50, the current sensing unit 60, and the foldback unit 70 are included.

The power supply unit 10 includes a first power supply terminal IN1 and a second power supply terminal IN2, and supplies power to the power folding mirror driving circuit 1. The power folding mirror driving circuit 1 may be supplied with a DC power supply, for example, a battery voltage of an automobile. When the battery voltage is applied to the first power terminal IN1 and the second power terminal IN2 is grounded, the motor M may operate in the forward direction. On the contrary, when the first power supply terminal IN1 is grounded and a battery voltage is applied to the second power supply terminal IN2, the motor M may operate in the reverse direction.

The abnormal signal blocking unit 20 may include a varistor ZNR and / or a capacitor C1. The abnormal signal blocking unit 20 blocks a surge signal and / or a noise signal introduced into the power folding mirror driving circuit 1 from the outside. Here, a surge signal refers to a transient signal that changes badly within a short time. Such a surge signal may occur in the process of turning on / off a switching circuit or interrupting an inductive load such as a relay.

The varistor ZNR protects a surge signal that may be generated externally and flow into the power folding driving circuit 1. Varistor (ZNR) is a two-terminal semiconductor device having a property that the resistance value is changed non-linearly by the voltage. The varistor ZNR has a very large resistance value up to the threshold voltage, and if it exceeds the threshold voltage, the varistor ZNR has a very small resistance value. Therefore, when a surge signal flows into the power folding mirror driving circuit 1, the resistance value of the varistor ZNR becomes very small, and a current flows toward the varistor ZNR, thereby absorbing the surge signal. As a result, elements such as transistors T1, T2, T3, T4, Q6, and Q7 in the power folding mirror driving circuit 1 can be protected from surge signals.

The capacitor C1 blocks noise that may be generated externally and may flow into the power folding driving circuit 1. When an AC signal that is noise is applied to the capacitor C1, the capacitor C1 may act as a short circuit to the noise. Therefore, it is possible to absorb the noise and to prevent the noise from flowing into the power folding drive circuit 1.

The bias voltage provider 30 may provide a turn-on bias voltage to the switching elements Q6 and Q7. The bias voltage provider 30 may include zener diodes Z1 and Z2 and resistors R2, R3, and R4.

The anodes of the Zener diodes Z1 and Z2 are connected to one end of the source and current detection resistors R7 and R8, which are one terminals of the switching elements Q6 and Q7, and the cathodes Z1 and Z2 of the Zener diodes are switched elements. The gate, which is a control terminal of Q6 and Q7, may be coupled to one of emitters and resistors R2 and R4 of the transistors T3 and T4. The resistors R3 and R4 may be coupled between one end of the buffer resistor R1 and the other terminal of the switching elements Q6 and Q7, respectively.

The resistor R2 may perform an impedance matching role in the power folding mirror driving circuit 1 operating in the forward operation mode and the reverse operation mode. In addition, the gate which is the control terminal of the switching element Q6 and the gate which is the control terminal of the switching element Q7 are shorted to each other so that the two switching elements Q6 and Q7 are not turned on at the same time or are not turned off at the same time. That is, only the switching element Q7 is turned on in the forward operation mode, and only the switching element Q6 is turned on in the reverse operation mode. On the other hand, the resistor R4 may limit the magnitude of the voltage applied to the node N3 in the forward operation mode, and the resistor R3 may limit the magnitude of the voltage applied to the node N4 in the reverse operation mode.

The switching unit 40 may include switching elements Q6 and Q7. The switching elements Q6 and Q7 may be turned on / off by a bias voltage. The switching elements Q6 and Q7 may be MOSFETs, for example, as shown. In addition, the substrate on which the MOSFET is formed may be internally connected to the source terminal.

The motor unit 50 may include a motor M, capacitors C4 and C5, and diodes D3 and D4. The motor M is a DC motor, and the switching elements Q6 and Q7 may be turned on and driven. When the switching element Q7 is turned on, the motor M may rotate in the forward direction, and when the switching element Q6 is turned on, the motor M may rotate in the reverse direction. Capacitors C4 and C5 are examples of an electromagnetic interference (EMI) reduction circuit to reduce electromagnetic waves of the motor, that is, noise generated in the motor. Capacitors C4 and C5 may have different capacitances. Since the frequency range of noise absorbed by the capacitors C4 or C5 is determined by the capacitance value, the capacitors C4 and C5 may reduce noises having different frequency ranges if they have different capacitances. The principle is the same as that of the capacitor C1 described above.

The diodes D3 and D4 control the direction in which current flows in the power folding mirror drive circuit 1. In the forward operation, the forward current flowing through the diode D3 flows through the switching element Q7. In the reverse operation, the reverse current flowing through the diode D4 flows through the switching element Q6.

The current sensing unit 60 may include current detection resistors R7 and R8. The current detection resistors R7 and R8 may be connected to the switching elements Q6 and Q7 so that a current flowing in the motor M may flow. The forward current may flow through the current detection resistor R8 and the reverse current may flow through the current detection resistor R7. When the motor is forcibly stopped, the current detector 60 may detect a current flowing in the motor M and output a sensing voltage. In particular, when the motor M is stopped, the stall current M flowing through the motor may be detected and provided to the foldback unit 70.

The fold-back unit 70 includes first transistors T1 and T2 including a first control terminal to which a sensing voltage is applied, and a second control terminal coupled to one terminal of the first transistor. Second transistors T3 and T4 and a buffer resistor R1 may be included. The transistors T2 and T4 are in the forward operating mode and can operate in a situation where the motor is forcibly stopped, and the transistors T1 and T3 are in the reverse operating mode and can be operated in the situation where the motor is forcibly stopped. The second transistors T3 and T4 of the foldback unit 70 may turn off the switching elements Q6 and Q7 by stepping down the bias voltage to a turn-off level when the sense voltage becomes higher than the cutoff voltage. Therefore, when the stall current flows, the foldback part 70 cuts off the power supply to the motor M, and can prevent motor burnout by the stall current.

The transistors T1 to T4 may be BJTs, the first transistors T1 and T2 may be npn transistors, and the second transistors T3 and T4 may be pnp transistors. In this case, the first control terminal of the first transistors T1 and T2 and the second control terminal of the second transistors T3 and T4 may each be a base, and one terminal of the first transistors T1 and T2 may be a collector. The emitter which is another terminal of the first transistors T1 and T2 may be connected to the ground terminals IN1 and IN2. The bases of the first transistors T1 and T2 and the collectors of the second transistors T3 and T4 may be coupled, and the emitters of the second transistors T3 and T4 are control terminals of the switching elements Q6 and Q7. The gate and the zener diodes Z1 and Z2 may be connected to the cathodes. In addition, the collectors of the first transistors T1 and T2 may be connected to both ends of the buffer resistor R1, respectively.

The buffer resistor R1 may perform an impedance matching role in the power folding mirror driving circuit 1 operating in the forward operation mode and the reverse operation mode. In addition, damage to the first transistors T1 and T2 may be prevented by limiting the magnitude of the current flowing through the first transistors T1 and T2.

The fold-back portion 70 may further include delay capacitors C2 and C3 and delay resistors R7 and R8. Delay capacitor C3 and delay resistor R8 operate in the forward operating mode, and delay capacitor C2 and delay resistor R7 operate in the reverse operating mode. One end of the delay capacitors C2 and C3 is coupled to the first control terminal of the first transistors T1 and T2 and one terminal of the second transistors T3 and T4 and the other of the second transistors T3 and T4. The terminal may be connected to the control terminals of the switching elements Q6 and Q7. The other end of the delay capacitors C2 and C3 may be connected to the ground terminal IN1 or IN2. When the transistors T1 to T4 are BJTs, one terminal of the second transistors T3 and T4 may be a collector. The delay resistors R7 and R8 may be coupled between the nodes N5 and N6 to which the sense voltages are output and the first control terminals of the first transistors T1 and T2.

Due to the configuration of the fold-back part 70, the second transistors T3 and T4 operate not only when the first transistors T1 and T2 operate in a saturation region but also when they operate in at least some active regions. Edo is turned on to cut off the power supplied to the motor (M). This will be described later in more detail with reference to the operation of the power folding mirror driving circuit 1.

2 and 3 to 5, the operation of the power folding mirror driving circuit in the forward mode of operation will be described. 3 and 4 are diagrams for explaining the operation of the circuit in the normal operation mode, the motor is normally driven. FIG. 5 is a diagram for describing an operation of a circuit in a forward operation mode in which a motor is forcibly stopped.

First, referring to FIG. 3, the battery voltage Vb is applied to the first power supply terminal IN1 and the ground voltage is applied to the second power supply terminal IN2. In the drawing, "+" is added to the first power supply terminal IN1 and "-" is added to the second power supply terminal IN2 so that the voltage level of the first power supply terminal IN1 is the second power supply terminal IN2. Indicates a relatively high voltage level.

When the power is supplied in this way, in a loop composed of the current detection resistor R7, the zener diode Z1, the resistor R2, the zener diode Z2, and the current detection resistor R8, the current detection resistor R7, A bias voltage is formed at the gate of the switching element Q7 through the zener diode Z1 and the resistor R2. As a result, when the gate voltage of the switching element Q7 becomes higher than the driving voltage, for example, 3 V or higher, the switching element Q7 may be turned on.

4, when the switching element Q7 is turned on, the first power supply terminal IN1, the diode D3, the motor M, the switching element Q7, the current detection resistor R8, And a closed loop including the second power supply terminal IN2. Therefore, power is supplied to the motor M, and the motor M rotates forward.

5, when the motor M is forcibly stopped, the stall current flows. The stall current flows through the current detection resistor R8, a voltage is generated across the current detection resistor R8, and the voltage of the node N5 is charged in the delay capacitor C3.

When the delay capacitor C3 is charged and the voltage applied to the node N7 becomes equal to or higher than the driving voltage of the first transistor T2, the first transistor T2 is biased to operate the first transistor T2. When the first transistor T2 operates, the collector voltage of the first transistor T2 is stepped down, whereby the second transistor T4 is biased to drive the second transistor T4. As a result, the emitter voltage of the second transistor T4 is stepped down, whereby the switching element Q7 is unbiased and turned when the gate voltage of the switching element Q7 falls below the driving voltage, for example, 3 V or less. Can be turned off. By turning off the switching element Q7, the power supply to the motor M is cut off and the stall current no longer flows to the motor M.

Here, the first transistor T2 is delayed and operated by a product (time constant) of the resistance value of the delay resistor R6 and the capacitance of the delay capacitor C3. For example, if the time constant is 1 s, the first transistor T2 operates after power is supplied to the motor M for approximately one.

The above time delay has the following effects. Although the mirror (see 9 in FIG. 1) does not rotate to the stop position (see P1 and P2 in FIG. 1), a situation may occur in which the mirror fails to rotate and the power supplied to the motor M is cut off. For example, foreign matter caught in the power folding mirror may prevent the mirror from rotating. In such a situation, the mirror may rotate by supplying power to the motor M for a time corresponding to the time constant.

On the other hand, in the circuit shown in FIG. 5, the stall current no longer flows in a situation in which the motor M is forcibly stopped, but the current may continuously flow in the foldback unit 70. Specifically, the closed loop is formed in the power folding mirror driving circuit 1 in the situation where the motor M is forcibly stopped.

One is the first power supply terminal IN1, the current detection resistor R7, the zener diode Z1, the resistor R2, between the emitter and the collector of the second transistor T4, the delay capacitor C3, and the second It is a closed loop composed of the power supply terminal IN2. The closed loop allows the first transistor T2 to be continuously biased so that current can continue to flow between the collector and emitter of the first transistor T2. The other is the first power supply terminal IN1, the current detection resistor R7, the zener diode Z1, the resistor R2, between the emitter and the base of the second transistor T4, and the collector of the first transistor T2. It is a closed loop composed between and emitters. Current may continue to flow in this closed loop.

As described above, even when the motor M is forcibly stopped, current flows continuously in the foldback unit 70. Specifically, after the power is cut off from the motor, positive transient noise generated from the outside may be introduced into the power folding mirror driving circuit 1. Due to such positive transient noise, the stall current may flow in the motor M by a positive transient timing even after the power supply to the motor M is cut off by the foldback unit 70. Alternatively, negative transient noise generated externally after the power is cut off from the motor may flow into the power folding mirror driving circuit 1. Such negative transient noise may cause a malfunction of the power folding mirror drive circuit 1. However, in the power folding mirror driving circuit 1 according to the exemplary embodiment of the present invention, even when the motor M is forcibly stopped, current may flow continuously in the foldback unit 70. Even when negative transient noise is introduced, the switching element Q7 is stably turned off to reduce the malfunction of the power folding mirror driving circuit 1 due to the stall current due to the positive transient noise and / or the negative transient noise.

The operation of the power folding mirror driving circuit in the reverse operation mode will be described with reference to FIGS. 2 and 6 to 8. 6 and 7 are diagrams for explaining the operation of the circuit in the reverse operating mode, the motor is normally driven. FIG. 8 is a diagram for describing an operation of a circuit in a reverse operating mode and in a situation where a motor is forcibly stopped. Since the operating principle of the power folding mirror drive circuit in the reverse operating mode is substantially the same as that in the forward operating mode, the descriptions that are substantially duplicated are omitted for convenience.

First, referring to FIG. 6, the battery voltage Vb is applied to the second power supply terminal IN2 and the ground voltage is applied to the first power supply terminal IN1. In the drawing, “+” is added to the second power supply terminal IN2 and “? Quot” is added to the first power supply terminal IN1 so that the voltage level of the second power supply terminal IN2 is equal to the first power supply terminal ( The voltage level is high relative to IN1).

When the power is supplied in this way, in a loop composed of the current detection resistor R8, the zener diode Z2, the resistor R2, the zener diode Z1, and the current detection resistor R7, the current detection resistor R8, A bias voltage is formed at the gate of the switching element Q6 through the zener diode Z2 and the resistor R2. As a result, when the gate voltage of the switching element Q6 becomes equal to or higher than the driving voltage, for example, 3 V or higher, the switching element Q6 may be turned on.

Next, referring to FIG. 7, when the switching element Q6 is turned on, the second power supply terminal IN2, the diode D4, the motor M, the switching element Q6, the current detection resistor R7, And a closed loop including the first power supply terminal IN1. Therefore, power is supplied to the motor M, and the motor M rotates in the reverse direction.

8, when the motor M is forcibly stopped, the stall current flows. The stall current flows through the current detection resistor R7, a voltage is generated across the current detection resistor R7, and the voltage of the node N6 is charged in the delay capacitor C2.

When the delay capacitor C2 is charged and the voltage applied to the node N8 becomes equal to or higher than the driving voltage of the first transistor T1, the first transistor T1 operates and immediately the second transistor T3 operates. As a result, the emitter voltage of the second transistor T3 is stepped down, whereby when the gate voltage of the switching element Q6 falls below the driving voltage, the switching element Q6 may be unbiased and turned off. By turning off the switching element Q6, the power supply to the motor M is cut off and the stall current no longer flows to the motor M. As shown in FIG. Here, the first transistor T1 operates by delaying the voltage corresponding to the product (time constant) of the resistance value of the delay resistor R5 and the capacitance of the delay capacitor C2.

Meanwhile, in the circuit shown in FIG. 8, the stall current no longer flows in a situation in which the motor M is forcibly stopped, but the current may continuously flow in the foldback unit 70. Since the operation principle and effect are substantially the same as those described with reference to FIG. 5, the detailed description is omitted for convenience.

According to the above-described power folding mirror and its driving circuit, the switching speed is relatively short, and the burnout of the motor due to the stall current can be prevented. In other words, even if a stall current occurs in the motor, the circuit is cut off within a short time, thereby protecting the motor.

Further, even when the driver operates the switch again while the driver operates the switch to fold or unfold the power folding mirror, the power folding mirror driving circuit may operate normally.

In addition, even when the magnitude of the voltage applied to the foldback part when the motor is stopped varies with temperature change, it is possible to stably cut off the power supply to the motor, thereby reducing the possibility of motor burnout by the stall current. Hereinafter, this will be described in detail with reference to FIG. 2.

The foldback portion 70 of the power folding mirror 1 according to the embodiment of the present invention is composed of a high side foldback circuit. That is, the collectors of the second transistors T3 and T4 for stepping down the bias voltage applied to the control terminals of the switching elements Q6 and Q7 of the foldback unit 70 to the turn-off level are connected to the ground terminal (IN2 in the forward operation mode). In reverse operation mode, it is not directly connected to IN1). The advantages obtained by the foldback unit 70 being constituted by the high side foldback circuit in this way are as follows.

The voltage level applied to the control terminals of the first transistors T1 and T2 is not constant according to the temperature change. For example, the resistance values of the current detection resistors R7 and R8 may vary according to the temperature change. Alternatively, the magnitude of the stall current flowing in the motor M may vary according to the temperature change. As a result, the voltage level applied to the control terminals of the first transistors T1 and T2 when the motor is forcibly stopped is equal to or less than the voltage level for operating the first transistors T1 and T2 in the saturation region, for example, 0.7 V or less. Voltage can be applied. In this case, the first transistors T1 and T2 operate in the active region. However, even in this case, a bias voltage of sufficient magnitude, for example, a bias voltage between 10 and 12 V may be applied to the control terminals of the second transistors T3 and T4. As a result, the second transistors T3 and T4 are turned on, so that the switching elements Q6 and Q7 can be turned off stably.

In summary, the high side foldback unit 70 may not only operate the first transistors T1 and T2 in the saturation region but also operate the second transistors T3 and T4 in the at least some active regions. It may be turned on to stably turn off the switching elements Q6 and Q7. Therefore, the power supply to the motor M can be interrupted stably, and the possibility of the motor M burnout by the stall current can be reduced.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

1 is a perspective view schematically showing the structure of a power folding mirror according to an embodiment of the present invention.

2 is a circuit diagram illustrating a power folding mirror driving circuit according to an exemplary embodiment of the present invention.

3 and 4 are diagrams for explaining the operation of the circuit in the normal operation mode, the motor is normally driven.

FIG. 5 is a diagram for describing an operation of a circuit in a forward operation mode in which a motor is forcibly stopped.

6 and 7 are diagrams for explaining the operation of the circuit in the reverse operating mode, the motor is normally driven.

FIG. 8 is a diagram for describing an operation of a circuit in a reverse operating mode and in a situation where a motor is forcibly stopped.

(Description of the main parts of the drawing)

10: power supply unit 20: abnormal signal blocking unit

30: bias voltage providing unit 40: switching unit

50: motor unit 60: current sensing unit

70: foldback part

Claims (14)

A switching element turned on / off by a bias voltage; A motor in which the switching element is turned on and driven; A current detector for sensing a current flowing through the motor and outputting a sensed voltage; And A fold-back comprising a first transistor having a first control terminal to which the sense voltage is applied and a second transistor having a second control terminal coupled to one terminal of the first transistor Including wealth, And the second transistor turns off the switching element by stepping down the bias voltage to a turn-off level when the sense voltage is equal to or greater than a cutoff voltage. According to claim 1, And a terminal of the first transistor is a collector, and a base of the first transistor and a collector of the second transistor are coupled to each other. According to claim 1, A delay capacitor charged with the sense voltage, wherein one end of the delay capacitor is coupled with the first control terminal of the first transistor and one terminal of the second transistor, And a second terminal of the second transistor is connected to a control terminal of the switching element. The method of claim 3, wherein And a delay resistor coupled between the node at which the sense voltage is output and the first control terminal of the first transistor. According to claim 1, An emitter of the second transistor is connected to a control terminal of the switching element, And a delay capacitor charged with the sense voltage, wherein one end of the delay capacitor is coupled with a base of the first transistor and a collector of the second transistor. According to claim 1, And the second transistor can be turned on when the first transistor operates in a saturation region and at least a portion of the active region. According to claim 1, And the current sensing unit is connected to the switching element and includes a current detection resistor through which a current flowing through the motor flows. According to claim 1, And a bias voltage providing unit configured to provide the switching device with the bias voltage at a turn-on level. According to claim 1, The bias voltage providing unit includes a first resistor and a zener diode, An anode of the zener diode is connected to one terminal of the switching element, And a cathode of the zener diode is coupled to a control terminal of the switching element and an emitter of the second transistor and one end of the first resistor. The method of claim 9, The bias voltage providing unit further includes a second resistor coupled between one end of the first resistor and the other terminal of the switching element. According to claim 1, And the first transistor is an npn transistor, and the second transistor is a pnp transistor. A switching element turned on / off by a bias voltage, a motor driven by the switching element turned on, a current sensing unit sensing a current flowing through the motor and outputting a sensing voltage, and a sensing unit to which the sensing voltage is applied. And a fold-back portion including a first transistor having a first control terminal and a second transistor having a second control terminal coupled with one terminal of the first transistor, wherein the second transistor is provided. A power folding mirror driving circuit for stepping down the bias voltage to a turn-off level when the sense voltage is equal to or greater than a cutoff voltage to turn off the switching element; An exercise transmission unit for transmitting a rotational motion of the motor; And And a mirror that rotates by the motion transfer unit. The method of claim 12, One terminal of the first transistor is a collector, the power folding mirror coupled to the base of the first transistor and the collector of the second transistor. The method of claim 12, A delay capacitor charged with the sense voltage, wherein one end of the delay capacitor is coupled with the first control terminal of the first transistor and one terminal of the second transistor, And a second terminal of the second transistor is connected to a control terminal of the switching element.

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