KR20090008754A - Emergency drive method in switch fail for dc/dc converter - Google Patents

Abstract

An emergency operation method in switch malfunction of a DC/DC converter is provided to perform the emergency operation of a LDC(Low-voltage DC Converter) by using a pair of switches of steady- state among four switches in switch open trouble. A controller delivers signals for switch fault diagnostics to a switch trouble detector in the abnormal operation of a LDC(ST1). According to the signal of the controller, the switch trouble detector authorizes PWM(Pulse Width Modulation) signal for checkup in a switch(ST2). The switch trouble detector makes the diagnosis of malfunction and type of the switch based on the current value detected from a current sensor connected to a switching unit input terminal. When one or two between a pair of switches among four switches operating to a pair are in open trouble and a remaindering pair of switches are steady, the PWM signal for drive is applied at the two steady switches(ST8). The emergency operation of the LDC is performed by on/OFF operation of the two steady switches.

Description

Emergency drive method in switch fail for DC / DC converter}

The present invention relates to an emergency operation method when the switch failure of the DC / DC converter, and more particularly to an emergency operation method when the switch failure of the low-voltage DC / DC converter mounted on a hybrid vehicle and a fuel cell vehicle.

Engine electric devices (starters, ignition devices, charging devices) and lighting devices are generally known as electric vehicles. However, in recent years, as vehicles become more electronically controlled, most systems including chassis electric devices are becoming electronic. to be.

Various electric appliances such as lamps, audio, heaters, and air conditioners installed in automobiles are supplied with power from the battery when the vehicle is stopped, and from the generator when driving the vehicle. Capacity is being used.

Recently, with the development of the information technology industry, a variety of new technologies (motor-powered steering, the Internet, etc.) aimed at increasing the convenience of automobiles have been applied to vehicles, and the development of new technologies that can make the most of the current automobile system will continue. It is a prospect.

As is known, low-voltage DC / DC converters charge 12V batteries (secondary batteries) and power 12V electric loads on behalf of alternators in electric vehicles such as hybrid vehicles (HEV), fuel cell vehicles, and fuel cell hybrid vehicles. (Low Voltage DC / DC Converter, LDC) is installed.

1 is a connection diagram of a low voltage DC / DC converter in a hybrid vehicle, wherein a low voltage DC / DC converter (LDC) 3 serving as an alternator of a general gasoline vehicle is a main battery (usually a high voltage battery of 144 V or more). The high voltage of the battery is lowered to supply a voltage of 12 V. The high voltage (DC) of the regenerative energy of the main battery (2) or the driving motor (1) is converted into 12 V (DC) to charge the auxiliary battery (12 V battery) (4). Or power the electrical load.

2 is a diagram illustrating a power conversion circuit and an operating state of a low voltage DC / DC converter (hereinafter, referred to as 'LDC') for a hybrid vehicle.

As shown, the hybrid vehicle LDC employs a full-bridge type power circuit structure for power conversion, and uses four switching elements S1 to S4 in the power circuit structure.

2, an input filter unit 10 including an input inductor L _in and an input capacitor C _in , and a switching unit (DC-to-AC conversion) 20 including switching elements S1 to S4. , A transformer (transformer) 30 for performing power conversion (decompression), including the transformer T, a rectifier (rectifier) 40 including a diode (D _o1 , D _o2 ), and an output inductor (L) _o ) and an output capacitor (C _o ), including an output filter unit (smoothing action) 50.

Among these, the switching unit 20 includes four full-bridge semiconductor switches S1 to S4 as switching elements, and a MOSFET is used as the semiconductor switch.

In the full bridge structure, the switches S1 to S4 operate on / off by a PWM signal applied from a PWM generator (not shown), and the PWM generator switches the switches S1 to S4. Generating and outputting a PWM signal for each component to perform switching control for each switch, a PWM IC for generating four PWM signals for turning on / off four switches S1 to S4 at regular intervals; It comprises a switching driving circuit unit for applying each PWM signal transmitted from the PWM IC to the corresponding switch.

In the LDC having the above-described configuration, each switch S1 to S4 is operated by applying a full bridge type phase shift control method as a switching method, and FIG. 3A is attached to the phase shift switching method in a normal operation state. And in Figure 3b.

Referring to FIG. 3A, the switch operation state is shown in the normal operation of the LDC. As illustrated, the switches S1 and S4 and the switches S2 and S3 operate in pairs.

The operation and control of each switch is caused by the PWM signal generated by the PWM generator and applied to the gate terminal of each switch, and applied from the PWM generator for on / off control of each switch S1 to S4 in the above-described LDC circuit structure. The on-off timing of each switch is controlled by the phase shifted PWM signal.

3B illustrates a phase shifted PWM signal applied to each of the switches S1 to S4 for on / off control in the normal operation state of the LDC, and to control on and off timings of the switches S1 to S4. Four phase shifted PWM signals S1 to S4 PWM are applied.

However, in the circuit structure of the LDC, which is a power converter, the most sensitive and failure-prone components are power devices, that is, semiconductor switches S1 to S4. In the past, even one of four switches having a full bridge structure is used. In the event of a failure, the LDC immediately turns off, so that the normal operation of the vehicle is impossible.

In other words, the full bridge structure used in the conventional LDC uses four semiconductor switches, and if any one switch failure occurs, the vehicle is not designed to operate itself. Therefore, if it is possible according to the type of failure, emergency operation of the LDC, it is necessary to have a way to enable the vehicle operation by the emergency operation of such LDC.

Therefore, the present invention has been invented to solve the above problems, it is determined that the type of failure at the time of switch failure, switch open failure according to the failure type of any one of the four switches of the switch operating in pairs is normal It is an object of the present invention to provide an emergency operation method in case of a switch failure of an LDC, which makes the LDC emergency by using normal switches and enables vehicle operation by the emergency operation of the LDC.

In order to achieve the above object, the present invention, in the hybrid vehicle and fuel cell vehicle, the switching unit is configured in the low voltage DC / DC converter (LDC) for converting the high power of the main battery to low power to provide a secondary battery and electric load As a method of emergency operation of the LDC in the event of a switch failure,

Transmitting a signal for causing the controller to perform switch failure diagnosis to a switch failure detection unit when a warning signal is generated due to an abnormal output state during the normal operation of the LDC; The switch failure detection unit receives a signal from the controller, generates a diagnostic PWM signal, applies the switch to the switch, and simultaneously receives a detection value of the current sensor connected to the input of the switching unit, and determines whether the switch has failed. A troubleshooting step of diagnosing the type; The switches S1 and S4 configured to operate in the switching unit and the switch failure detection unit in S2 and S3 are one or both of the pairs of open faults according to the diagnosis result of the switch fault detection unit, and the other pair of switches In a normal state, an emergency operation step of applying a driving PWM signal to two normally determined switches, such that the LDC is emergency operated by turning on and off the two normal switches; Provides emergency operation methods.

Here, preferably, when it is diagnosed that a short circuit occurs in accordance with the diagnosis result of the fault diagnosis step, the switch failure detection unit outputs a signal to the controller so that the LDC is turned off by the controller; It is done.

In the fault diagnosis step, (a) the switch fault detection unit first applies a diagnostic PWM signal to the switches S1 and S4 operating in pairs, and compares the current value of the detected current sensor with a preset maximum limit value and minimum limit value. Making a step; (b) If the current value of the current sensor is less than the minimum limit value, it is determined that one or both of the switches S1 and S4 are open faults, and then the PWM for diagnostics is applied to the switches S2 and S3 in which the switch fault detection unit operates in pairs. Applying a signal and comparing the detected current value of the current sensor with a preset maximum limit value and minimum limit value; (c) Here, if the current value of the current sensor is more than the minimum limit and less than the maximum limit, it is determined that the normal state of the switches S2 and S3.

Here, preferably, (d) if the current value of the current sensor from the step (a) is greater than the maximum limit value, diagnosing that a short circuit has occurred; characterized in that it further comprises a.

(B ') From the step (a), if the current value of the current sensor is greater than or equal to the minimum limit and less than or equal to the maximum limit, it is determined that the switches S1 and S4 are in a normal state, and the switch failure detection unit operates in pairs. And applying a diagnostic PWM signal to S3 and comparing the detected current value of the current sensor with a preset maximum limit value and minimum limit value. (c ') wherein if the current value of the current sensor is smaller than the minimum limit value, determining that one or both of the switches S2 and S3 are open faults.

Here, preferably, (d ') diagnosing that a short circuit occurs when the current value of the current sensor is greater than the maximum limit value from the step (b').

The driving PWM signal includes a phase-shifted PWM signal for each switch output by a PWM generator, and simultaneously switches between two switches normally determined based on a switch failure information signal transmitted from the switch failure detection unit by a PWM emergency controller. A PWM signal converted to turn on and off; The PWM emergency control unit may select the two normally determined switches based on the switch fixed information signal of the switch failure detection unit to apply the driving PWM signal.

According to the emergency operation method of the switch failure of the present invention having the above characteristics, in the full-bridge method using the four switches at the time of switch open failure after determining the type of failure, determine the location of the failed switch when the switch failure occurs The inverter is operated by adjusting the PWM signal for driving and controlling the switch to operate in a half-bridge method using two switches in the steady state, and thus, the vehicle can be operated by the emergency operation of the converter.

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

The present invention relates to an emergency operation method in the case of a switch failure of a low voltage DC / DC converter installed in a hybrid vehicle and a fuel cell vehicle, and includes a high voltage (DC) of regenerative energy by a main battery (high voltage battery) and a driving motor. To emergency operation of low voltage DC / DC converter (hereinafter referred to as 'LDC') that converts power to a secondary battery (12V battery) and provides it to the electric field load (12V electric field load). will be.

In particular, the present invention relates to a technology for emergency operation of the LDC so that the vehicle can be driven when an open circuit occurs in one or two of the four semiconductor switches constituting the switching unit in the LDC.

In the present invention, a switch in a normal state in a full-bridge method using four switches in case of a switch open failure is determined after determining a type of failure (open or short circuit) when a switch failure occurs. The PWM signal, which is a switch driving and control signal, is adjusted to operate in a half-bridge manner using two.

4 is a configuration diagram for diagnosing a switch failure in the process of performing the LDC emergency operation according to the present invention, and FIG. 5 is a flowchart illustrating the LDC emergency operation process according to the present invention.

6A and 6B are state diagrams showing a switch operation state (operation state of a normally determined switch) during an LDC emergency operation according to the present invention. In the present invention, a separate operation performed for the LDC emergency operation upon detecting a switch failure is performed. A switching function (hard switching function) is added, and FIGS. 6A and 6B illustrate a state in which a switch normally determined by the separate switching function for emergency operation is turned on when a switch failure is detected.

The example of FIG. 6A illustrates a state in which the turn-on operation of the switches S1 and S4 determined to be normal when the failure of any one or both of the switches S2 and S3 is detected in the switching unit of the LDC is performed. The state where the turn-on operation of the switches S2 and S3 determined as the normal state at the time of detecting the failure of any one or both of S4 is shown.

7 is a view showing a PWM signal (hard switch PWM signal) applied for driving and controlling each switch during an LDC emergency operation according to the present invention, wherein each PWM signal is output of a PWM generator for an LDC emergency operation. PWM signal converted from the signal (switching control signal in emergency operation), and in the drawing, 'S1 PWM' and 'S4 PWM' are the switches S1 and S4 normally determined at the time of detecting the failure of one or both of the switches S2 and S3. For the PWM signal applied to, 'S2 PWM' and 'S3 PWM' represent the PWM signal applied to the switches S2 and S3 which are normally determined at the time of detecting the failure of either or both of the switches S1 and S4.

The converted PWM signal of FIG. 7 for each switch is a switch driving to which the PWM emergency control unit, which will be described later, converts the existing phase shifted PWM signal output by the PWM generator 60 during the LDC emergency operation to be applied to the switch in the steady state. This is a control signal.

8 is a schematic view showing an example of a configuration of a PWM emergency control unit for performing an emergency operation process according to the present invention, and FIG. 9 is a phase shifted final applied to a gate end of each switch when the switch is in a normal state. The PWM signal and the phase shifted PWM signal when the switch failure is determined are converted into a hard switching method by the PWM emergency control unit to convert the PWM signal in the emergency state (hard switch PWM signal) which is finally applied to the gate terminal of each switch. It is shown together.

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

In the LDC emergency operation according to the present invention, the signals 'S1 PWM', 'S2 PWM', 'S3 PWM', and 'S4 PWM' of FIG. 7 are not simultaneously applied to the four switches S1 to S4. The failure type is determined and the LDC is emergency operated by using the normal switches when any one of the four switches operating in pairs is normal with the switch open failure according to the failure type.

To this end, in the present invention, a switch failure detection function and a hard switching function for the LDC emergency operation are added. As shown in FIGS. 4 and 8, a switch failure detection unit 80 for detecting a switch failure type and a switch, and a switch On the basis of the output signal of the switch fault detection unit 80 indicating fault information, the PWM signal for each phase shifted switch output by the PWM generator 60 is converted into a switching control signal for emergency operation, that is, a hard switch PWM signal. The PWM emergency control unit 61 to be applied to the gate terminal of the normally determined switch is added.

In addition, a current sensor 70 is provided at an input terminal of the LDC switching unit for detecting and diagnosing a failure of the switch failure detection unit 80, and the current sensor 70 may input an output signal, that is, a current detection signal. It is connected to the switch failure detection unit (80).

In the present invention, when the switch failure detection unit 80 determines the switch of the failure state of the four switches (S1 ~ S4), in order to operate in a half-bridge (half-bridge) method using only two normally operating switches, PWM The emergency control unit 61 converts the phase shifted PWM signal applied from the PWM generator 60 into a PWM signal for emergency operation as shown in FIGS. 7 and 9 and applies it to only two switches in the steady state.

Here, the PWM generator 60 generates four phase shifted PWM (PWD) signals, which are the same as in the conventional normal operation, during the emergency operation, even in an emergency operation due to a switch failure, and the PWM generator 60 outputs the same. A PWM signal is applied to the PWM emergency control unit 61 and converted into a PWM signal during emergency operation as shown in FIGS. 7 and 9. In the PWM emergency control unit 61, a switch failure is detected from an output signal of the switch failure detection unit 80. After determining the state, the PWM signal of the PWM generator 60 is converted into a PWM signal for emergency operation, and the switch of the steady state is selected from the output signal of the switch fault detection unit 80 to apply the converted PWM signal.

In the switching unit having four full-bridge semiconductor switches S1 to S4 in the LDC, the switches S1 and S4 and the switches S2 and S3 operate in pairs, and by using the operation principle, the switch failure detection unit 80 If a failure of either or both of the switches S1 and S4 is detected, the corresponding PWM signal for emergency operation of FIGS. 7 and 9 is applied to another switch pair in the normal state, that is, the switches S2 and S3, and vice versa. And detecting a failure of any one or both of S3 and S3, a corresponding PWM signal for the phase operation of FIGS. 7 and 9 is applied to the switches S1 and S4.

Referring to Figure 5, when the switch failure detection process and the emergency operation process according to the present invention will be described in order, first, when the LDC is operating in a normal state, when an abnormal phenomenon occurs, such as abnormality in the LDC output waveform, LDC dedicated The controller 90 outputs a warning signal to an external controller such as an HCU (ST1), and at the same time, the controller 90 switches to the failure detection mode and diagnoses each switch failure in the switch failure detection unit 80 (failure occurs. Status, type, and detection of faulty switch).

The LDC used in the hybrid vehicle and the fuel cell vehicle monitors the state of the output by itself, and when an abnormality occurs, the dedicated controller 90 generates a warning signal and transmits it to an external controller, and automatically turns off the LDC at the same time as the warning signal is generated. It has a function to make it.

In the present invention, such a function is used, but when a failure occurs, the switch failure detection unit 80 performs the switch failure diagnosis after switching to the failure detection mode without immediately turning off the LDC by the warning signal of the LDC.

Referring to the diagnosis logic of the switch failure detection unit 80 for detecting switch failure, after switching to the failure detection mode, the switch failure detection unit 80 first generates a diagnostic PWM signal and applies it to the switches S1 and S4, respectively ( ST2) At this time, the current value I (or lower voltage value) detected and output by the current sensor 70 is compared with a preset maximum limit value Imax and minimum limit value Imin (ST3).

Here, when the detected current value I is larger than the maximum limit value Imax (Imax <I), the switch fault detection unit 80 recognizes that a short circuit occurs, and in this case, a controller having an LDC off function The controller 90 immediately turns off the LDC by outputting a signal indicating the occurrence of a short circuit in which the PWM switching control of the switches S1 and S4 is impossible (LDC STOP) (ST11).

If the detected current value I is smaller than the minimum limit value Imin (I <Imin), it is recognized as a switch open fault and searches for the next switch portion to find an available switch portion to determine whether emergency operation is possible. Judge.

That is, the diagnostic PWM signal is applied to the switches S2 and S3, respectively (ST4), and then the current value I (or below voltage value) detected and output by the current sensor 70 is set in advance to the maximum limit value Imax and The minimum limit value Imin is compared (ST5).

Here, when the current value I detected by the current sensor 70 is greater than or equal to the minimum limit value Imin and less than or equal to the maximum limit value Imax (Imin ≦ I ≦ Imax), the switches S2 and S3 may be in a normal state. It is determined that a failure of any one or both of the switches S1 and S4 has occurred, and generates a switch failure information signal (ST6), and outputs this switch failure information signal to the PWM emergency control unit 61.

At this time, the PWM emergency control unit 61 based on the switch failure information signal output from the switch failure detection unit 80, the PWM signal applied by the PWM generator 60 after that phase shifted PWM signal as shown in Figs. At the same time as the signal is converted (ST7), a steady state switch is selected to apply each converted PWM signal to the selected switches S2 and S3 (ST8).

As described above, the switches S2 and S3 are repeatedly turned on and off at regular intervals by the PWM signals applied to the switches S2 and S3. In this case, the simultaneous turn-on and simultaneous turn-off of the two switches are repeatedly performed. It will be in the same state as 6b.

As a result, the AC power applied from the switching unit in which the on / off operation of the switches S2 and S3 is repeated is decompressed through the converter as in the prior art, and finally converted into the necessary 12V DC power through the rectifying unit and the output filter unit to be provided as a 12V battery. Will be.

As described above, the LDC is turned off when a short circuit occurs, but when the circuit is opened due to a switch failure, the LDC is emergency operated to supply normal power to the 12V battery. The half-bridge method using the bay allows the LDC to operate as an emergency operation.

Of course, the state in which the switches S1 and S4 are turned on by the diagnostic PWM signal, and the state in which the switches S2 and S3 are turned on by the diagnostic PWM signal are the same as those of FIGS. 6A and 6B, respectively. The current sensor 70 will detect the current value.

If, in ST6, the detected current value I is less than the minimum limit value Imin (I <Imin) or greater than the maximum limit value Imax (I> Imax), like the switches S1 and S4, the switch S2 And in the case of switch S3 either or both of the failure state, at this time, the switch failure detection unit 80 outputs a signal indicating that the PWM switching control of the switch is not possible to the controller 90 having the LDC off function This immediately turns off the LDC (LDC STOP) (ST11).

In ST3, when the detected current value I is above the minimum limit value Imin and below the maximum limit value Imax (Imin≤I≤Imax), a diagnostic PWM signal is also generated and applied to the switches S2 and S3, respectively. Next, the current value I detected by the current sensor 70 is then compared with the maximum limit value Imax and the minimum limit value (ST10).

If greater than the maximum limit value Imax in the ST10 (I> Imax), the fault detection circuit unit outputs a signal indicating that a short circuit occurs that PWM switching control of the switches S2 and S3 is impossible to the controller 90 having the LDC off function. This immediately turns off the LDC (LDC STOP) (ST11).

Here, when the current value I detected by the current sensor 70 is smaller than the minimum limit value Imin (I <Imin), the switches S1 and S4 are in a steady state or any one or two of the switches S2 and S3. It is determined that all of the failures have occurred, generates a switch failure information signal (ST12), and outputs this switch failure information signal to the PWM emergency control unit 61.

At this time, the PWM emergency control unit 61 based on the switch failure information signal output from the switch failure detection unit 80, the PWM signal applied by the PWM generator 60 after that phase shifted PWM signal as shown in Figs. At the same time of converting to a signal (ST13), a switch in a steady state is selected and each converted PWM signal is applied to the selected switches S1 and S4 (ST14).

As described above, the switches S1 and S4 are repeatedly turned on and off at regular intervals by the PWM signals applied to the switches S1 and S4. In this case, the simultaneous turn-on and simultaneous turn-off of the two switches are repeatedly performed. It will be in the same state as 6a.

As a result, the AC power applied from the switching unit in which the on / off operation of the switches S1 and S4 is repeated is decompressed through the converter as in the prior art, and finally converted into the necessary 12V DC power through the rectifying unit and the output filter unit and provided as a 12V battery. Will be.

As described above, the LDC is turned off when a short circuit occurs, but when the circuit is opened due to a switch failure, the LDC is emergency operated to supply normal power to the 12V battery. The half-bridge method using the bay allows the LDC to operate as an emergency operation.

As described above, in the LDC emergency operation process according to the present invention, after the switch failure detection unit 80 is switched to the failure detection mode by the warning signal output from the LDC, four full-bridge semiconductor switches are paired in the LDC. By using the principle that the switch failure detection unit 80 is divided into the switch S1 and S4, and S2 and S3 by sequentially applying the diagnostic PWM signal to the set value of the current value detected by the current sensor 70 By comparing with, it is possible to determine a failure state of any one or two of the switches S1 and S4, or to determine a failure state of any one or both of the switches S2 and S3.

When the switch failure diagnosis process is completed as described above, as in the configuration example of the PWM emergency control unit 61 shown in FIG. 8, the switch failure detection unit 80 outputs a signal to the PWM emergency control unit 61 to output the PWM emergency control unit 61. ) Converts the phase shifted steady state PWM signal applied from the PWM generator 60 into a PWM signal for emergency operation, and selects a normally determined switch to apply the converted PWM signal.

As such, the PWM emergency control unit 61 converts the PWM signal in the normal state based on the output signal of the switch failure detection unit 80 to convert the PWM signal for emergency operation, and at the same time, the switches S1 and S4 or S2 and S3 which are normally determined are And the converted PWM signal is applied to the corresponding switch, and the switch normally determined by the applied converted PWM signal is turned on and off at a predetermined period so that emergency operation of the LDC is performed.

8 shows an example of a configuration of the PWM emergency control unit 61 as an emergency PWM operation circuit, and the PWM generator 60 outputs a phase shifted PWM signal for each switch in the same manner as in the prior art, and this phase The PWM emergency control unit 61 converts the shifted PWM signal into a PWM signal as shown in FIGS. 7 and 9 based on the output signal of the switch failure detection unit 80, and simultaneously selects a switch that is normally determined, and then switches each of the corresponding switches. The emergency operation of applying the converted PWM signal is performed.

The PWM emergency controller 61 has a configuration in which a plurality of AND gates are used in the example of FIG. 8, but the phase output from the PWM generator 60 based on the signal of the switch failure detection unit 80 as described above. Various configurations can be implemented if the circuit or logic is configured to have an emergency operation function of converting the shifted PWM signal into a PWM signal for emergency operation and then selectively applying the switch to a normally determined switch.

In the illustrated example, the PWM emergency control unit 61 converts a phase shifted PWM signal, which is applied in the same manner as in the prior art, into a hard switch PWM method based on the switch failure information signal of the switch failure detection unit 80 for each switch. Normally determined based on the PWM conversion logic unit 62 outputting the converted PWM signal as shown in FIGS. 7 and 9 and the switch failure information signal (fault: 0, normal: 1) of the switch failure detection unit 80 The switch selection logic unit 63 selects a switch and finally applies a PWM signal of the PWM conversion logic unit 62 to the switch.

9 shows a phase shifted PWM signal in a steady state which is finally applied to each switch in a steady state on the upper side, and a PWM signal converted to a hard switching method in an emergency state, that is, at the time of failure detection, on the lower side. The PWM signal that is last applied to each switch for LDC emergency operation is shown.

The switch failure detection unit 80 is connected to the gate terminals of the switches S2 and S3 by the switch selection logic unit 63 of the PWM emergency control unit 61 when it is determined that any one or both of the switches S2 and S3 are in a failure state. A low signal (O) indicating a fault condition is applied to each connected AND gate, while a high signal ("1") indicating a steady state is applied to each AND gate connected to the gate terminals of switches S1 and S4. A PWM signal (a PWM signal converted to hard switching in an emergency state) is applied to only S1 and S4 periodically and repeatedly.

In addition, the switch failure detection unit 80 determines that any one or both of the switches S1 and S4 is in a failure state, and the gate terminals of the switches S1 and S4 in the switch selection logic unit 63 of the switch PWM emergency control unit 61. A low signal ("0") indicating a fault condition is applied to each AND gate connected to the gate, and a high signal "1" indicating a steady state is applied to each AN gate connected to the gate terminals of the switches S2 and S3. In the end, a PWM signal (a PWM signal converted to a hard switching method in an emergency state) is applied to the switches S2 and S3 periodically.

Of course, as described above, when the switch S1 or S4 fails together in a state where a failure of the switch S2 or S3 is detected by the switch failure detection unit 80, the controller 90 according to the signal of the switch failure detection unit 80. ) Will turn off the LDC.

In this way, in the present invention, the failure type is determined at the time of the switch failure, and the LDC is used by using the normal switches when any one of the four switches operating as a pair is normal with the switch open failure according to the failure type. Emergency operation is made, and vehicle operation is enabled by the emergency operation of the LDC.

1 is a connection diagram of a low voltage DC / DC converter in a hybrid vehicle,

2 is a view showing a power conversion circuit and an operating state of a low-voltage DC / DC converter for a hybrid vehicle,

3A is a diagram illustrating a switch operation state of a low voltage DC / DC converter for a hybrid vehicle;

3B is a diagram illustrating a phase shifted PWM signal applied to each switch of a low voltage DC / DC converter for a hybrid vehicle;

4 is a configuration diagram for diagnosing a semiconductor switch failure during an emergency operation of a low voltage DC / DC converter according to the present invention;

5 is a flow chart showing an emergency operation of the low voltage DC / DC converter according to the present invention,

6A and 6B are state diagrams showing a switch operation state during an emergency operation of a low voltage DC / DC converter according to the present invention;

7 is a view showing a PWM signal applied to each switch in the emergency operation according to the present invention,

8 is a schematic diagram showing a configuration example of a PWM emergency control unit for performing an emergency operation process according to the present invention;

9 is a phase shifted PWM signal which is finally applied to the gate terminal of each switch when the switch is in a normal state, and a PWM signal in an emergency state in which a phase shifted PWM signal is converted to a hard switching method when determining a switch failure. The figure which shows.

<Explanation of symbols for the main parts of the drawings>

10: input filter unit 20: switching unit

30: converter 40: rectifier

50: output filter 60: PWM generator

61: emergency control unit 62: PWM conversion logic unit

63: switch selection logic section 70: current sensor

80: switch failure detection unit 90: controller

S1 ~ S4: Switch

Claims (7)

As a method of emergency operation of the LDC in the event of a switch failure in a low voltage DC / DC converter (LDC) which converts the high power of the main battery into low power in a hybrid vehicle and a fuel cell vehicle and provides the auxiliary battery and the electric load. , Transmitting a signal for causing the controller to perform switch failure diagnosis to a switch failure detection unit when a warning signal is generated due to an abnormal output state during the normal operation of the LDC; The switch failure detection unit receives a signal from the controller, generates a diagnostic PWM signal, applies the switch to the switch, and simultaneously receives a detection value of the current sensor connected to the input of the switching unit, and determines whether the switch has failed. A troubleshooting step of diagnosing the type; According to the diagnosis result of the switch failure detection unit in the switches S1 and S4 and S2 and S3 configured to operate the switching unit, either or both of the pairs of switches are open and the other pair of switches are normal. A state in which the driving PWM signal is applied to two normally determined switches so that the LDC is emergency operated by turning on and off the two normal switches; Emergency operation when the switch failure of the DC / DC converter comprising a. The method according to claim 1, When it is diagnosed that a short circuit occurs according to the diagnosis result of the fault diagnosis step, the switch fault detection unit outputs a signal to the controller to turn off the LDC by the controller; Emergency operation in case of switch failure of the converter. The method according to claim 1 or 2, The fault diagnosis step, (a) first applying a diagnostic PWM signal to the switches S1 and S4 operating as a pair of switch failure detection units, and comparing the current value of the detected current sensor with a preset maximum limit value and minimum limit value; (b) If the current value of the current sensor is less than the minimum limit value, it is determined that one or both of the switches S1 and S4 are open faults, and then the PWM for diagnostics is applied to the switches S2 and S3 in which the switch fault detection unit operates in pairs. Applying a signal and comparing the detected current value of the current sensor with a preset maximum limit value and minimum limit value; (c) where the current value of the current sensor is greater than or equal to the minimum limit and less than or equal to the maximum limit value, determining that the switches S2 and S3 are in a normal state. The method according to claim 3, and (d) diagnosing that a short circuit has occurred if the current value of the current sensor is greater than the maximum limit value from step (a). The method according to claim 3, (b ') From the step (a), if the current value of the current sensor is greater than or equal to the minimum limit and less than the maximum limit, it is determined that the switches S1 and S4 are in a normal state, and then the switch S2 and the switch fault detection unit operate in pairs. Applying a diagnostic PWM signal to S3 and comparing the current value of the detected current sensor with a preset maximum limit value and minimum limit value; (c ') where the current value of the current sensor is less than the minimum limit value, determining that one or both of the switches S2 and S3 are open faults; Emergency operation method when the switch failure of the DC / DC converter, characterized in that it further comprises. The method according to claim 5, and (d ') diagnosing that a short circuit occurs if the current value of the current sensor is greater than the maximum limit value from step (b'). . The method according to claim 1, The driving PWM signal is a phase-shifted PWM signal for each switch output by the PWM generator, and the PWM emergency control unit simultaneously turns on two switches normally determined based on the switch failure information signal transmitted from the switch failure detection unit at regular intervals, A PWM signal converted to turn off; And said PWM emergency control unit selects two normally determined switches based on the switch fixed information signal of said switch failure detection unit and applies said driving PWM signal.

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