KR100310645B1 - Over-current protection circuit using desaturation in IPM - Google Patents

Abstract

The present invention implements a protection circuit against overcurrent by using the inherent characteristics of a general-purpose switching device in the development of a standard IPM, so that the protection circuit can be operated in real time in the event of overcurrent, and the switching saturation can be reduced to reduce the switching shock during turn-off. The present invention relates to an overcurrent protection circuit of the used IPM, and the present invention drives the IGBT by buffering the IGBT drive signal in the buffer unit. When the IGBT is driven, the reverse saturation voltage detector detects whether an overcurrent flows through the IGBT. When the overcurrent is detected, the control signal generator generates the turn-off signal and the surge voltage prevention signal of the IGBT. Surge voltage prevention means to softly turn off the IGBT in the overcurrent according to the surge voltage prevention signal to prevent the generation of surge voltage to reduce the switching shock.

Description

Over-current protection circuit using desaturation in IPM}

The present invention relates to an overcurrent protection circuit in an IPM, and in particular, in the development of a standard IPM, by implementing a protection circuit against overcurrent by using a unique characteristic of a general-purpose switching device, the protection circuit operates in real time in case of overcurrent and is turned off The present invention relates to an overcurrent protection circuit of a power module using reverse saturation to reduce switching shock.

In general, in the development of the IPM for supplying and controlling the power supply, a protection circuit is provided to prevent the device connected to the rear end from being damaged by overcurrent or short circuit current.

1 is an example of a protection circuit applied to a conventional IPM for protecting a device in the event of an overcurrent or a short circuit current as described above.

As shown, the driving of the sense IGBT 2 is controlled according to a sense gate bipolar transistor (IGBT) 2 having an overcurrent detection function and a control signal input from the outside. When the overcurrent is sensed in the sense IGBT 2, the dedicated drive IC 1 turns off the driving of the sense IGBT 2 immediately.

The overcurrent protection circuit in the conventional IPM configured as described above controls the driving of the sense IGBT 2 in accordance with a control signal input from the ASIC-dedicated drive IC 1 externally. That is, when the control signal input from the outside is a drive signal, the dedicated drive IC 1 operates to drive the sense IGBT 2. If the external control signal is a drive off signal, the dedicated drive IC 1 turns off the driving of the sense IGBT 2. This operation controls the driving of the sense IGBT 2.

The above operation is an operation state when the input power source is normal, and if an abnormality occurs in the input power source, that is, an over current occurs, the sense IGBT 2 detects it and converts the overcurrent detection value into a voltage. To the dedicated drive IC 1.

The sense IGBT 2 is an IGBT in which an overcurrent detection terminal is added to a commercially available IGBT, and the added detection terminal detects a part of the current IC between the collector and the emitter according to the detection ratio Ratio. That is, the detection ratio is set so that about 1/1000 of the current (IC) flowing between the collector and the emitter flows through the detection terminal. Therefore, when 1000 mA of current flows through the collector and the emitter, Current will flow. The current detected in this way is converted into a voltage by the resistor R2 and input to the dedicated drive IC 1.

Although not shown in the drawing, the dedicated drive IC 1 compares the voltage detected by the overcurrent with a preset reference voltage using a voltage comparator to determine whether the overcurrent is large or small. That is, when the voltage detected by the detection terminal is larger than the reference voltage, it is determined as an overcurrent, and in this case, the driving signal of the sense IGBT 2 is immediately interrupted to turn off the driving of the sense IGBT 2.

However, since the overcurrent protection circuit applied to the conventional IPM uses a dedicated drive IC made of sense IGBT and ASIC, it has a high development cost and a long development period.

In addition, since the sense IGBT is turned off by using a dedicated drive IC after the overcurrent is detected by the sense IGBT, it takes a long time to turn off the sense IGBT during overcurrent, and its function is weak as a fundamental protection circuit against overcurrent. There was this.

An object of the present invention for solving the problems that occur in the overcurrent protection circuit applied to the conventional IPM as described above is to implement a protection circuit for overcurrent by using the unique characteristics of the general-purpose switching device in the development of the standard IPM, real-time when overcurrent It is an object of the present invention to provide an overcurrent protection circuit of an IPM using a reverse saturation that allows a protection circuit to operate.

Another object of the present invention for solving the above problems of the prior art is to implement a protection circuit against overcurrent by using the inherent characteristics of the general-purpose switching device in the development of the standard IPM, to reduce the switching shock during turn-off It is to provide an overcurrent protection circuit of IPM using a reverse saturation.

1 is a configuration diagram of an overcurrent protection circuit applied to a conventional IPM;

2 is a configuration diagram of an overcurrent protection circuit of an IPM using reverse saturation according to the present invention.

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

10: waveform conversion unit 20: buffer unit

30: desaturation voltage detector 40: control signal generator

50: surge voltage prevention unit 60: voltage discharge unit

The present invention for achieving the above object is, in the IPM for supplying and controlling the operating power, the waveform conversion means for converting the waveform of the power control signal input from the outside into a constant waveform, and the control obtained by the waveform conversion means Buffering means for logically combining, buffering and outputting a power control signal according to whether the signal and an overcurrent are detected, and desaturating voltage detecting means for detecting a desaturation voltage of an IGBT whose driving is controlled according to a control signal output from the buffering means; Control signal generation means for generating the power supply control signal and a surge voltage prevention signal according to the desaturation voltage detection signal output from the desaturation voltage detection means, and the IGBT according to the surge voltage prevention signal generated by the control signal generation means. And a surge voltage preventing means for softly reducing the voltage accumulated at the base end of the It is characterized by.

As an additional feature of the present invention for achieving the above object, the desaturated voltage detecting means includes a current source for outputting a sense current for detecting whether there is an overcurrent, a first and a level for setting a current output from the current source; A high voltage diode which generates a difference between a second diode, a current flowing through the collector of the IGBT, and a current set by the first and second diodes as a desaturation detection voltage, a voltage source for setting a reference voltage, And a voltage comparator for comparing the reference voltage set by the voltage with the reverse saturation detection voltage obtained by the high voltage diode and outputting the result as an overcurrent detection value.

As another additional feature of the present invention for achieving the above object, the control signal generating means prevents the power supply control signal and the surge voltage according to the signal output from the desaturation voltage detecting means and the signal output from the waveform converting means. RS flip-flop for generating a control signal.

As another additional feature of the present invention for achieving the above object, the surge voltage preventing means is a switching element is controlled to drive according to the surge voltage prevention signal output from the control signal generating means, and the turn of the switching element It consists of a resistor and a capacitor which gradually discharge the voltage accumulated at the base terminal of the IGBT by the time constant at on time.

As another additional feature of the present invention for achieving the object as described above further includes a voltage discharge means for bypassing the voltage applied to the desaturated voltage detection means to ground in accordance with a control signal output from the waveform conversion means. To be configured.

The above object and various advantages of the present invention will become more apparent from the preferred embodiments of the present invention described below with reference to the accompanying drawings by those skilled in the art.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention according to the technical spirit as described above in detail.

2 is a block diagram of an overcurrent protection circuit of an IPM using reverse saturation according to the present invention.

As shown, the waveform conversion unit 10 for converting the waveform of the power control signal (/ Vin) input from the outside into a regular waveform, the control signal obtained from the waveform conversion unit 10 and the power control according to whether or not overcurrent detection A buffer unit 20 for logically combining, buffering and outputting a signal, a desaturation voltage detector 30 for detecting a desaturation voltage of an IGBT whose driving is controlled according to a control signal output from the buffer unit 20, and the inverse The control signal generator 40 generating the power control signal and the surge voltage prevention signal according to the desaturation voltage detection signal output from the saturation voltage detector 30, and the surge voltage prevention signal generated by the control signal generator 40. According to the control signal output from the surge voltage suppressor 50 and the waveform converter 10, which softly reduces the voltage accumulated at the base end of the IGBT. It consists of the voltage to a voltage discharger 60 to by-pass to ground.

The operation of the overcurrent protection circuit of the IPM using reverse saturation according to the present invention configured as described above is as follows.

The diodes D1 (D2) and the Schmitt trigger element 11 in the waveform converter 10 make the level of the drive control signal / Vin input from the outside at a constant level, and simultaneously shape and output the waveform. The driving control signals output in this way are input to the buffer unit 20 and the voltage discharge unit 60, respectively.

Since the driving control signal in the normal state is a square wave, the voltage discharge unit 60 inverts the phase of the square wave in the inverter IV2, and the switching element Q4 switches according to the driving control signal inverted in phase. This is controlled. That is, when the IGBT driving signal is the high signal 5V, the output waveform of the inverter IV2 becomes the low signal 0V, and thus the switching element Q4 is turned off.

Meanwhile, the buffer unit 20 logically multiplies the phase inverted signal of the driving control signal output from the logical conversion element 21 from the waveform conversion unit 10 and the power control signal output from the control signal generator 40. Here, in the normal state, since the power supply control signal is always a high signal, the output of the logical product element 21 is determined according to the driving control signal. If the output of the logical multiplication device 21 is a high signal, the first switching device Q1 is turned on to flow a current of a predetermined level to the base of the IGBT to turn on the IGBT. When the first switching device Q1 is turned on, the second switching device Q2 is turned off by the output of the inverter IV1. Alternatively, the first switching device Q1 is turned off. When the second switching device (Q2) is turned on by the output of the inverter IV1 to bypass the base terminal voltage of the first switching device (Q1) and the cathode terminal voltage of the diode (D3) to the ground Do it.

Next, in the normal state of the turned-on IGBT, Vce (voltage between the collector and emitter) increases linearly in proportion to Ic, and overcurrent Ic flows.

In addition, the reverse saturation voltage detector 30 outputs a sense current by the current source 31, the level of the sense current is set by the diodes D5 and D6, and the collector of the IGBT in the high voltage diode D4. The current difference between the current flowing through and the level set by the diodes D5 and D6 is obtained and input to the non-inverting terminal + of the voltage comparator 32. At this time, the reference voltage (Vref) set by the voltage source 33 is input to the inverting terminal (-) of the voltage comparator 32, the voltage comparator 32 compares the input voltage of the two terminals (+,-) The result is printed. That is, when the input voltage is in a normal state, since the desaturation detection voltage is lower than the reference voltage Vref, the output signal of the voltage comparator 32 becomes a low signal. In contrast, when the overcurrent occurs, the desaturation voltage flows. Since the desaturation voltage is greater than the reference voltage Vref, the output signal of the voltage comparator 32 becomes a high signal.

When the high signal is output from the voltage comparator 32 due to the overcurrent, a high signal is input to the S terminal of the RS flip-flop 41 in the control signal generator 40, and thus a high signal is also output from the output terminal Q. do. At this time, a low signal is output to the output terminal / Q, and the output of the logical product element 21 in the buffer unit 20 is also a low signal by the low signal output to the / Q terminal, and the IGBT is turned off.

When the IGBT is turned off, a surge voltage is generated by rapidly discharging the voltage stored in the base terminal of the IGBT. In order to remove the surge voltage generated in this way, the switching element Q3 in the surge voltage preventing unit 50 is turned on by the high signal output from the Q terminal of the RS flip-flop 41 to switch the capacitor C1. The voltage accumulated at the base end of the IGBT by this switching operation gradually discharges to the ground by the resistor R1 and the time constant R1 * C1 of the capacitor C1. That is, by implementing a soft turn-off during the turn-off of the IGBT, it is possible to prevent the generation of the surge voltage by di / dt generated when the overcurrent is blocked.

While the invention has been shown and described in connection with specific embodiments thereof, it will be appreciated that various modifications and changes can be made without departing from the spirit and scope of the invention as indicated by the claims. Anyone who owns it can easily find out.

As described above, the present invention implements an overcurrent protection circuit using a general-purpose IGBT and a switching IC, thereby simplifying the manufacturing process, shortening the development period, and reducing the development cost. .

In addition, by turning off the IGBT in a soft turn-off operation, it is possible to suppress the generation of surge voltage, thereby increasing the reliability of the product.

Claims (5)

In the IPM to supply and control the operating power, Waveform conversion means for converting a waveform of a power supply control signal input from the outside into a regular waveform; Buffering means for logically combining, buffering, and outputting a control signal obtained from the waveform converting means and a power supply control signal according to whether or not overcurrent is detected; Desaturation voltage detection means for detecting a desaturation voltage of an IGBT whose driving is controlled according to a control signal output from the buffering means; Control signal generation means for generating said power supply control signal and a surge voltage prevention signal in accordance with a desaturation voltage detection signal output from said desaturation voltage detection means; And a surge voltage preventing means for softly reducing the voltage accumulated at the base end of the IGBT according to the surge voltage preventing signal generated by the control signal generating means. The method of claim 1, The desaturation voltage detecting means includes a current source for outputting a sense current for detecting an overcurrent, first and second diodes for setting a level of a current output from the current source, a current flowing through the collector of the IGBT, and the first source. A high voltage diode which generates a difference between the currents set by the first and second diodes as a reverse saturation detection voltage, a voltage source for setting a reference voltage, a reference voltage set by the voltage source and a reverse saturation detection voltage obtained by the high voltage diode The over-current protection circuit of the power module using the reverse saturation, characterized in that for comparing and comparing the output value with the over-current detection value. The method of claim 1, The control signal generating means comprises an RS flip-flop for generating a power supply control signal and a surge voltage prevention control signal according to a signal output from the desaturation voltage detecting means and a signal output from the waveform converting means. Overcurrent protection circuit of power module using The method of claim 1, The surge voltage preventing means gradually reduces the voltage accumulated at the base terminal of the IGBT by a switching element whose driving is controlled according to the surge voltage preventing signal output from the control signal generating means, and a time constant at turn-on of the switching element. An overcurrent protection circuit of a power module using reverse saturation comprising a resistor and a capacitor for discharging. The method of claim 1, And a voltage discharging means for bypassing the voltage applied to the desaturated voltage detecting means to ground in accordance with a control signal output from the waveform converting means.