JP2008270548A - Driving unit for photocoupler, power converting device, and driving method for photocoupler - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress a delay in signal propagation by a photocoupler while improving the life of the photocoupler. <P>SOLUTION: Output signal monitoring circuits 21 and 22 monitor the levels of output signals SU2 and SD2 from photocouplers FU1 and FU2, and transmit the result of the monitoring to current control circuits 23 and 24 on the side of a control circuit 1 via photocouplers FU4 and FU5, respectively. When receiving the result of monitoring of the levels of output signals SU2 and SD2 from the photocouplers FU1 and FU2 from the output signal monitoring circuits 21 and 22, the current control circuits 23 and 24 controls forward currents flowing through light-emitting diodes on the input side of the photocouplers FU1 and FU2, based on signal levels on the output side of the photocouplers FU1 and FU2. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a photocoupler driving device, a power converter, and a photocoupler driving method, and more particularly, to a current conversion efficiency (CTR: current) of a photocoupler that transmits a signal while insulating between a high voltage side and a low voltage side. The present invention is suitable for application to a method of driving a photocoupler while estimating (Transfer Ratio).

In recent vehicle equipment, in order to achieve high efficiency and energy saving measures, a step-up / down converter and an inverter are mounted on a drive system of an electric motor that generates drive force.
FIG. 12 is a block diagram showing a schematic configuration of a vehicle drive system using a conventional buck-boost converter.
In FIG. 12, the vehicle drive system includes a power source 1101 that supplies power to the buck-boost converter 1102, a buck-boost converter 1102 that boosts and boosts the voltage, and an inverter that converts the voltage output from the buck-boost converter 1102 into a three-phase voltage. 1103 and an electric motor 1104 for driving the vehicle are provided. Note that the power source 1101 can be configured by a power supply voltage from an overhead wire or a battery connected in series.

  When the vehicle is driven, the step-up / down converter 1102 boosts the voltage of the power source 1101 (eg, 280 V) to a voltage suitable for driving the electric motor 1104 (eg, 750 V) and supplies the boosted voltage to the inverter 1103. Then, by turning on / off the switching element, the voltage boosted by the buck-boost converter 1102 is converted into a three-phase voltage, current is passed through each phase of the electric motor 1104, and the switching frequency is controlled to control the vehicle. The speed of the can be changed.

  On the other hand, at the time of braking of the vehicle, the inverter 1103 performs a rectifying operation by performing on / off control of the switching element in synchronization with the voltage generated in each phase of the electric motor 1104 to convert it into a DC voltage, and then the buck-boost converter. 1102. The step-up / down converter 1102 can perform a power regeneration operation by reducing the voltage (eg, 750 V) generated from the electric motor 1104 to the voltage (eg, 280 V) of the power source 1101.

FIG. 13 is a block diagram showing a schematic configuration of the buck-boost converter of FIG.
In FIG. 13, a buck-boost converter 1102 includes a reactor L for storing energy, a capacitor C for storing charge, switching elements SW1 and SW2, and switching elements SW1 and SW2 for energizing and interrupting current flowing into the inverter 1103. Control circuits 1111 and 1112 are provided for generating control signals instructing conduction and non-conduction, respectively.

  The switching elements SW1 and SW2 are connected in series, and a power source 1101 is connected to a connection point of the switching elements SW1 and SW2 via a reactor L. Here, the switching element SW1 is provided with an IGBT (Insulated Gate Bipolar Transistor) 1105 that performs a switching operation in accordance with a control signal from the control circuit 1111. The flywheel diode D1 that flows a current in a direction opposite to the current flowing in the IGBT 1105 is the IGBT 1105. Connected in parallel.

  Further, the switching element SW2 is provided with an IGBT 1106 that performs a switching operation in accordance with a control signal from the control circuit 1112, and a flywheel diode D2 that flows a current in a direction opposite to the current flowing in the IGBT 1106 is connected in parallel to the IGBT 1106. The collector of the IGBT 1106 is connected to both the capacitor C and the inverter 1103.

FIG. 14 is a diagram showing a waveform of a current flowing through the reactor of FIG. 13 during the boosting operation.
14, the step-up operation, IGBT1105 switching element SW1 Then on (conductive), a current I flows through the reactor L through the IGBT1105, energy ^LI 2/2 is stored in the reactor L.
Next, when the IGBT 1105 of the switching element SW1 is turned off (non-conducting), a current flows through the flywheel diode D2 of the switching element SW2, and the energy stored in the reactor L is sent to the capacitor C.

On the other hand, in the step-down operation, IGBT1106 switching element SW2 is turned on (conducting) Then a current I flows through the reactor L through the IGBT1106, energy ^LI 2/2 is stored in the reactor L.
Next, when the IGBT 1106 of the switching element SW2 is turned off (non-conducting), a current flows through the flywheel diode D1 of the switching element SW1, and the energy stored in the reactor L is regenerated to the power source 1101.

Here, the voltage of the step-up / step-down can be adjusted by changing the ON time (ON Duty) of the switching element, and the approximate voltage value can be obtained by the following equation (1).
V _L / V _H = ON Duty (%) (1)
However, _VL is a power supply voltage, _VH is a voltage after step-up / step-down, and ON Duty is a ratio of a conduction period to a switching cycle of the switching elements SW1 and SW2.
Here, the actual variation of the load, since there is such fluctuations in the power supply voltage V _L, monitors the voltage V _H after buck, so that the voltage V _H after buck becomes a target value, the switching element SW1 , SW2 ON time (ON Duty) is controlled.

Further, the control circuits 1111 and 1112 that are grounded to the vehicle body casing are at low pressure, and the arm side that is connected to the switching elements SW1 and SW2 is at high pressure. Therefore, even if an accident such as destruction of the switching elements SW1 and SW2 occurs, the arm side is connected to the control circuit 1111 using a photocoupler or a pulse transformer so that the human body is not exposed to danger. Signals are exchanged while being electrically insulated from 1112.
Here, photocouplers are being used in vehicles in recent years because they are smaller and cheaper than pulse transformers.

FIG. 15 is a diagram illustrating a configuration of a PWM signal transmission circuit using a photocoupler.
In FIG. 15, the photocoupler FC is generated by an infrared light emitting diode PD1 that emits infrared light by a forward current If, a light receiving diode PD2 that receives infrared light emitted from the infrared light emitting diode PD1, and a light receiving diode PD2. A phototransistor M2 is provided which performs a current amplification operation using the photocurrent as a base current. A resistor R28 is connected in parallel to the infrared light emitting diode PD1, and the cathode of the infrared light emitting diode PD1 is connected to the field effect transistor M1 through the resistor R29 and the resistor R00 in order. The resistor R28 is provided to prevent the infrared light emitting diode PD1 from being turned on by a dark current such as a leakage current or a noise current that flows when the field effect transistor M1 is turned off.

The collector of the phototransistor M2 is connected to the power supply voltage Vcc2 via the load resistor RL, and the output signal Vout output via the collector of the phototransistor M2 is sent to the IGBT drive IC 30 via the resistor R _LPF. Entered.
Here, the IGBT drive IC 30 has a pull-up function of the input terminal of the IGBT drive IC 30, a binarization function of the output signal Vout from the photocoupler FC, a gate drive function of the IGBT, and an overcurrent / overtemperature protection function of the IGBT. Is provided. In the pull-up function of the input terminal of the IGBT drive IC 30, a steady current I _{LV-IC of} about 80 μA at the maximum from the current mirror circuit in the IGBT drive _{IC 30} is externally connected via the resistor R _LPF for the purpose of improving noise resistance. If a greater amount of current is not drawn by the photocoupler FC, the threshold value for turning on the IGBT is not reached.

When the input signal Vin is input to the gate of the field effect transistor M1, the forward current If flows to the infrared light emitting diode PD1, and infrared light is emitted. The infrared light emitted from the infrared light emitting diode PD1 is received by the light receiving diode PD2, and a photocurrent corresponding to the infrared light flows to the base of the phototransistor M2. When a photocurrent flows to the base of the phototransistor M2, a collector current Ic flows to the phototransistor M2, and a steady current ILV _-IC is discharged from the current mirror circuit in the IGBT drive _{IC 30} to the outside through the resistor R _LPF. Thus, the current flowing through the load resistor RL having one end connected to the power supply voltage Vcc2 is Ic-I _LV-IC . Then, the change in the voltage at the other end of the load resistor RL accompanying the change in the collector current Ic is input to the IGBT drive IC 30 via the resistor R _LPF as the output signal Vout from the photocoupler FC.

Here, the forward current If flowing in the infrared light emitting diode PD1 of the photocoupler FC can be expressed by the following equation (1).
If = (Vp−Vf) / (R29 + R00 + Ron) −Vf / R28 (1)
However, Vf is the forward voltage drop of the infrared light emitting diode PD1, and Ron is the on-resistance of the field effect transistor M1.
The collector current Ic of the phototransistor M2 that flows by the forward current If can be expressed by the following equation (2).
Ic = If × initial guarantee CTR × CTR life deterioration (2)

On the other hand, a steady current I _LV-IC for pull-up is discharged to the input terminal of the IGBT drive _{IC 30} through the resistor R _LPF , and the current flowing through the load resistor RL having one end connected to the power supply voltage Vcc 2 is Ic Since −I _LV-IC , the collector potential Vc of the phototransistor M2 can be expressed by the following equation (3).
Vc = Vcc2−RL × (Ic−I _LV−IC ) (3)
Since the collector potential Vc of the phototransistor M2 is input to the IGBT drive IC 30 via the resistor R _LPF , the value of the output signal Vout from the photocoupler FC input to the IGBT drive IC 30 is (4 ) Expression.
Vout = Vcc2−RL × (Ic−I _LV−IC ) + R _LPF × I _LV−IC (4)

Here, the input / output characteristics of the single photocoupler FC can be defined by current conversion efficiency (CTR: Current Transfer Ratio), that is, Ic / If. When designing a circuit using the photocoupler FC, (1) temperature characteristics of the current amplification factor hfe of the phototransistor M2, (2) lifetime deterioration of the luminous efficiency of the infrared light emitting diode PD1, (3) current It is necessary to consider points such as variations in conversion efficiency.
In the fields of industry, railways, automobiles, etc., the photocoupler FC is continuously used over a long period of time in an environment of −40 to + 100 ° C. For example, when cumulative use is performed at 100 ° C. for 15000 hours. Also, the value of the load resistance RL is determined so as to operate even at −40 ° C. while corresponding to the deterioration of the current conversion efficiency and the temperature dependence.

FIG. 16 is a diagram showing the collector / emitter voltage dependence of the current conversion efficiency when the forward current If flowing through the light emitting diode of the photocoupler at 20 ° C. is used as a parameter.
In FIG. 16, when the collector / emitter voltage Vce of the phototransistor M2 is 0.5 V or more, the current conversion efficiency of the photocoupler FC is substantially constant regardless of the forward current If.
FIG. 17 is a diagram showing the temperature dependence of the current conversion efficiency when the collector current Ic of the phototransistor with respect to the forward current If flowing through the light-emitting diode of the photocoupler is used as a parameter.
In FIG. 17, the current conversion efficiency of the photocoupler FC decreases as the temperature decreases, and the cause of this is the temperature characteristic of the current amplification factor hfe of the phototransistor M2.

FIG. 18 is a graph showing the temporal characteristics of current conversion efficiency when the forward current If flowing in the light emitting diode of the photocoupler is used as a parameter.
In FIG. 18, the current conversion efficiency of the photocoupler FC decreases depending on the forward current If of the light emitting diode PD1, the environmental temperature, and the cumulative usage time. In particular, when the continuous usage time of the photocoupler FC exceeds 1000 hours, The decrease in current conversion efficiency appears significantly. The main cause of the decrease in the current conversion efficiency of the photocoupler FC is a decrease in the light emission efficiency of the light emitting diode PD1. The forward current If of the light emitting diode PD1 is large, and the current conversion efficiency is significantly decreased as the environmental temperature is higher. .
Note that the characteristics of the photocoupler FC vary greatly depending on the lot and the solid, and as a minimum guarantee, it is necessary to set 8% at −40 ° C. as a guide.
Further, in the PWM signal transmission circuit using the photocoupler FC of FIG. 15, a propagation delay occurs between the input signal Vin and the output signal Vout.

FIG. 19 is a diagram illustrating the definition of propagation delay times of an input signal and an output signal in a PWM signal transmission circuit using a photocoupler.
19, the falling time from the rising of the forward current If flowing through the light emitting diode PD1 of FIG. 15 to the low level threshold VINL of the output signal Vout is defined as TPHL, and the forward current If flowing through the light emitting diode PD1 of FIG. TpLH is defined as the rise time from when the output signal Vout falls to when the output signal Vout reaches the high level threshold value VINH.

  Here, the potential at the input terminal when the output of the IGBT drive IC 30 in FIG. 15 is inverted is VINL when the output is high, and VINH when the output is low, and no malfunction occurs when the output of the IGBT drive IC 30 is inverted. In order to do so, hysteresis is provided as VINL ≦ VINH. In order for the output of the IGBT drive IC 30 to become high level, the value of the output signal Vout from the photocoupler FC input to the IGBT drive IC 30 is Vout ≦ VINL, and for the output of the IGBT drive IC 30 to become low level, Vout ≧ VINH. It is necessary to satisfy the relationship.

20A is a diagram illustrating the propagation delay time characteristic of the photocoupler with respect to the load resistance RL, and FIG. 20B is a diagram illustrating the propagation delay time characteristic of the photocoupler with respect to the ambient temperature Ta.
In FIG. 20, the fall time TPHL by the photocoupler FC hardly changes regardless of the load resistance RL and the ambient temperature Ta, but the rise time TpLH increases as the load resistance RL and the ambient temperature Ta increase. .

  As a result, as the load resistance RL and the ambient temperature Ta increase, the low level period of the output signal Vout from the photocoupler FC becomes longer and the IGBT on period becomes longer, so that the upper and lower arms of the inverter are short-circuited. Causes destruction of the IGBT. For this reason, a dead time is provided in the gate signal of the IGBT to prevent the upper and lower arms of the inverter from being short-circuited.

FIG. 21 is a diagram showing a method for setting the dead time of the gate signal of the IGBT.
In FIG. 21, the dead time DT1 is set so that the gate voltage of the lower arm rises after the fall of the gate voltage of the upper arm, and the gate voltage of the upper arm changes with respect to the fall of the gate voltage of the lower arm. The dead time DT2 is set so as to rise with a delay.
The dead times DT1 and DT2 need to be set with a margin with respect to the difference ΔT between the fall time TPLL and the rise time TpLH in order to be able to cope with the characteristic variation of the photocoupler FC and the usage environment. is there. On the other hand, if the dead times DT1 and DT2 are increased, the variable range of the duty ratio of the PWM signal is narrowed and the control response of the output of the IGBT is greatly affected. Therefore, it is usually set to about 5 μs.

22 shows the temperature dependence of the forward voltage of the light emitting diode, FIG. 23 shows the temperature dependence of the on-resistance of the field effect transistor, and FIG. 24 shows the temperature of the forward current flowing through the light emitting diode. It is a figure which shows dependency.
In FIG. 22, it can be seen that the forward voltage of the infrared light emitting diode PD1 of FIG. 15 has a negative temperature characteristic. In FIG. 23, it can be seen that the on-resistance Ron of the field-effect transistor M1 of FIG. 15 has a positive temperature characteristic. As a result, as shown in FIG. 24, the forward current If of the infrared light emitting diode PD1 of FIG. 15 has a positive temperature characteristic, and it can be seen that the forward current If increases as the temperature increases.

FIG. 25 is a diagram showing the estimated lifetime with respect to the ambient temperature of the photocoupler when the forward current is used as a parameter.
In FIG. 25, it can be seen that the estimated lifetime of the photocoupler becomes shorter as the environmental temperature becomes higher and becomes shorter as the forward current If of the infrared light emitting diode PD1 becomes larger.
On the other hand, as shown in FIG. 17, the current conversion efficiency of the photocoupler FC increases as the environmental temperature increases. Therefore, if the current flowing through the load resistor RL in FIG. The forward current If of the external light emitting diode PD1 can be reduced.

Further, for example, in Patent Document 1, based on the signal level on the output side of the photocoupler when driving the light emitting element on the input side in the photocoupler that is incorporated in the device and used for signal transmission and reception, A method for detecting the operational state of a photocoupler is disclosed.
Further, for example, in Patent Document 2, a speed-up capacitor is connected in parallel to a resistor for holding current limiting provided in a current-carrying path of the light-emitting diode, and a resistor is connected in series to the speed-up capacitor. A method for individually setting a peak current and a hold current flowing in a light emitting element of a photocoupler with a simple circuit configuration is disclosed.
JP 2004-37155 A JP-A-8-149085

However, in the PWM signal transmission circuit using the conventional photocoupler FC, as shown in FIG. 24, the forward current If of the infrared light emitting diode PD1 increases as the environmental temperature increases. In addition, there is a problem that the estimated life of the photocoupler FC is shortened.
Further, it is necessary to set in advance so that the forward current If of the infrared light emitting diode PD1 is increased so that the PWM signal can be normally transmitted even if the current conversion efficiency of the photocoupler FC is lowered. . For this reason, in the initial operation period in which the current conversion efficiency of the photocoupler FC is hardly reduced, the forward current If of the infrared light emitting diode PD1 exceeds the originally required value, and as shown in FIG. There was a problem of promoting the life deterioration of the coupler FC.
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a photocoupler driving device, a power converter, and a photocoupler driving method capable of improving the lifetime of the photocoupler while suppressing the propagation delay of the signal by the photocoupler. It is.

In order to solve the above-described problem, according to the photocoupler driving device according to claim 1, the output level is monitored by the output signal monitoring means for monitoring the signal level on the output side of the photocoupler, and the output signal monitoring means. Current control means for controlling the forward current of the light emitting diode flowing on the input side of the photocoupler based on the signal level.
According to the photocoupler drive device of claim 2, the inclination detecting means for detecting the rising or falling inclination of the signal on the output side of the photocoupler on the output side of the photocoupler, and the inclination detecting means Current control means for controlling the forward current of the light emitting diode flowing on the input side of the photocoupler based on the rising or falling slope of the signal on the output side of the photocoupler detected in this way. .

  Further, according to the photocoupler driving device according to claim 3, the inclination detecting means includes level detecting means for detecting whether the signal on the output side of the photocoupler has reached a plurality of threshold values of different levels. And a time interval measuring means for measuring a time difference when the signal on the output side of the photocoupler reaches a plurality of threshold values of different levels, and the current control means is configured such that the signal on the output side of the photocoupler The forward current of the light emitting diode that flows on the input side of the photocoupler is controlled based on the time difference when a plurality of threshold values at different levels are reached.

According to the photocoupler drive device of claim 4, the delay time calculating means for calculating the delay time at the rise or fall of the signal on the output side of the photocoupler, and the delay time calculating means Current control means for controlling the forward current of the light emitting diode flowing to the input side of the photocoupler based on the calculated delay time at the rise or fall of the signal on the output side of the photocoupler. To do.
The photocoupler drive device according to claim 5 is characterized in that the signal on the output side of the photocoupler is a signal on which a photocurrent of a phototransistor constituting the photocoupler acts.

The photocoupler drive device according to claim 6 further comprises a variable voltage source that varies a forward voltage applied to a light emitting diode on the input side of the photocoupler, wherein the current control means includes the variable The forward current of the light emitting diode flowing on the input side of the photocoupler is controlled by controlling the voltage of the voltage source.
Further, according to the photocoupler drive device of claim 7, when the voltage value of the variable voltage source exceeds a value corresponding to the allowable pulse current of the light emitting diode of the photocoupler, an alarm is generated. Features.

  Further, according to the power conversion device of claim 8, a pair of switching elements that are connected in series so as to operate for the upper arm and the lower arm, respectively, to energize and interrupt the current flowing into the load, A control circuit that generates a control signal that instructs conduction and non-conduction of the switching element, a drive circuit that drives a control terminal of the switching element based on the control signal, and the control circuit and the drive circuit are insulated. And a photocoupler that is provided for each switching element and transmits a signal between the control circuit and the drive circuit, and a signal on the output side of the photocoupler has reached a plurality of threshold levels at different levels. Level detection means for detecting whether or not the signal on the output side of the photocoupler reaches a plurality of threshold values at different levels. The forward current of the light-emitting diode that flows on the input side of the photocoupler is controlled based on the time difference when the interval measurement means and the signal on the output side of the photocoupler reach a plurality of threshold values of different levels And a current control means.

  According to the photocoupler driving method of claim 9, the step of measuring the time difference when the signal on the output side of the photocoupler reaches a plurality of threshold values of different levels, and the output side of the photocoupler And controlling the forward current of the light-emitting diode flowing on the input side of the photocoupler based on the time difference when the signal reaches a plurality of threshold values of different levels.

  As described above, according to the present invention, the signal level on the output side of the photocoupler is monitored, so that the photocoupler can be controlled according to the ambient temperature in which the photocoupler is used or the deterioration of the current conversion efficiency of the photocoupler. It becomes possible to control the forward current of the light emitting diode flowing on the input side. For this reason, the forward current of the light emitting diode on the input side of the photocoupler is reduced as the environmental temperature is increased, and in the initial operation period in which the current conversion efficiency of the photocoupler is less decreased, the light emitting diode on the input side of the photocoupler It is possible to limit the forward current to a necessary value, and it is possible to improve the life of the photocoupler while suppressing the signal propagation delay by the photocoupler.

Hereinafter, a photocoupler driving apparatus according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a block diagram showing a schematic configuration of an intelligent power module for a buck-boost converter to which a photocoupler driving device according to an embodiment of the present invention is applied.
In FIG. 1, the intelligent power module for the buck-boost converter generates control signals for instructing conduction and non-conduction of switching elements SWU, SWD and switching elements SWU, SWD for energizing and interrupting the current flowing into the load, respectively. A circuit 1 is provided.

Here, the control circuit 1 can be configured by a CPU, a logic IC, or a system LSI on which the logic IC and the CPU are mounted. Then, the control circuit 1, the buck-boost command value SP based on the comparison result by the _{V H} comparator 4, _{V H} comparator 4 for comparing the PWM signal SD6 generated by _{V H} detection circuit 13, the gate drive Of the PWM signal SU1, SD1 for the signal, the gate signal generator 5 for controlling the duty ratio, the low pass filter 6 for removing unnecessary high frequency components from the PWM signal SD6 generated by the _VH detection circuit 13, and the photocouplers FU1, FU2. Current control circuits 23 and 24 for controlling the forward current of the light emitting diodes flowing on the input side of the photocouplers FU1 and FU2 based on the signal level on the output side are provided.

  The control circuit 1 can generate the gate drive PWM signals SU1 and SD1 that operate the switching elements SWU and SWD by PWM control. In the PWM control, on / off of the switching elements SWU and SWD in each phase arm can be controlled according to a voltage comparison between a voltage command value on a sine wave and a carrier wave (typically a triangular wave). The basic component of the set of the high level period corresponding to the ON period of the switching element SWU on the upper arm 2 side and the low level period corresponding to the ON period of the switching element SWD on the lower arm 3 side is constant for a certain period The duty ratio can be limited to a sine wave.

  The switching elements SWU and SWD are connected in series so as to operate for the upper arm 2 and the lower arm 3, respectively. The switching element SWU is provided with an IGBT 7 that performs a switching operation according to the gate signal SU3, and a flywheel diode DU1 that allows a current to flow in a direction opposite to the current that flows in the IGBT 7 is connected in parallel to the IGBT 7. The chip on which the IGBT 7 is formed has a main circuit in which the emitter current of the IGBT 7 is shunted through the temperature sensor using the VF change of the diode DU2 due to the temperature change of the chip as a measurement principle, and the resistors RU1 and RU2. A current sensor for detecting current is provided.

  Further, the switching element SWD is provided with an IGBT 8 that performs a switching operation in accordance with the gate signal SD3, and a flywheel diode DD1 that flows a current in a direction opposite to the current flowing in the IGBT 8 is connected in parallel to the IGBT 8. The chip on which the IGBT 8 is formed includes a temperature sensor that uses the VF change of the diode DD2 due to the temperature change of the chip as a measurement principle, and the emitter current of the IGBT 8 is shunted through the resistors RD1 and RD2, and the main circuit. A current sensor for detecting current is provided.

As the switching elements SWU and SWD, for example, a power MOSFET or a bipolar transistor may be used in addition to the IGBTs 7 and 8.
On the upper arm 2 side, a gate driver 9 for generating a gate signal SU3 for driving the control terminal of the IGBT 7 is provided, an overheat detection signal SU5 from the temperature sensor, and an overcurrent detection signal SU4 from the current sensor. An IGBT protection circuit 10 that protects the IGBT 7 by controlling the driving of the gate driver 9 is provided.

On the upper arm 2 side, an output signal monitoring circuit 21 for monitoring the signal level of the output signal SU2 from the photocoupler FU1 and transmitting the monitoring result to the current control circuit 23 on the control circuit 1 side is provided.
On the lower arm 3 side, a gate driver 11 for generating a gate signal SD3 for driving the control terminal of the IGBT 8 is provided, an overheat detection signal SD5 from the temperature sensor, and an overcurrent detection signal SD4 from the current sensor. An IGBT protection circuit 12 that protects the IGBT 8 by controlling the driving of the gate driver 11 is provided.

On the lower arm 3 side, an output signal monitoring circuit 22 for monitoring the signal level of the output signal SD2 from the photocoupler FD1 and transmitting the monitoring result to the current control circuit 24 on the control circuit 1 side is provided.
Further, on the lower arm 3 side, a V _H detection circuit 13 that converts an output signal V _H from the IGBT 7 into a PWM signal SD 6 is provided. The V _H detection circuit 13 includes a triangular wave generator 14 that generates a triangular wave, and an IGBT 7. the output signal from the output signal dividing circuit 16 to the V _H divide, IGBT 7 which has been level-adjusting section 15 and the level adjustment adjusts the level of the output signal V _H from IGBT 7 which is divided by the voltage dividing circuit 16 from A comparison circuit 17 is provided that generates the PWM signal SD6 based on the comparison result between V _H and the triangular wave generated by the triangular wave generator.

Further, photocouplers FU1 to FU5 are inserted between the control circuit 1 side grounded to the vehicle body casing and the upper arm 2 side and the lower arm 3 side that are at high pressure. Signals can be exchanged while being electrically insulated from the upper arm 2 side and the lower arm 3 side using FU1 to FU5.
Then, the gate signal generator 5 generates the gate drive PWM signals SU1 and SD1 for instructing the conduction or non-conduction of the IGBTs 7 and 8, respectively. The gate drive PWM signals SU1 and SD1 are supplied to the photocouplers FU1 and FU2, respectively. Insulated and transmitted to the gate drivers 9 and 11, respectively, and insulated and transmitted to the drive devices 21 and 22, respectively.

The gate drivers 9 and 11 generate gate signals SU3 and SD3 based on the gate drive PWM signals SU1 and SD1, respectively, and drive the control terminals of the IGBTs 7 and 8, respectively, thereby switching the IGBTs 7 and 8 respectively. Let
Here, the overheat detection signals SU5 and SD5 output from the temperature sensor are input to the IGBT protection circuits 10 and 12, respectively, and the overcurrent detection signals SU4 and SD4 output from the current sensor are input to the IGBT protection circuits 10 and 12, respectively. Each is entered. Then, the IGBT protection circuits 10 and 12 notify the gate drivers 9 and 11 of this when the thresholds that the IGBTs 7 and 8 do not break are exceeded. When the gate drivers 9 and 11 receive notifications from the IGBT protection circuits 10 and 12 that the IGBTs 7 and 8 have exceeded the threshold values that do not destroy, the gate drivers 9 and 11 stop generating the gate signals SU3 and SD3, respectively. Cut off the current flowing through

The output signal V _H from the IGBT 7 is input to the V _H detection circuit 13, and after the level adjustment is performed by the voltage dividing circuit 16 and the level adjustment unit 15, the output signal V _H is compared with the triangular wave generated by the triangular wave generator 14. According to the voltage comparison, the comparison circuit 17 generates the PWM signal SD6. The PWM signal SD6 generated by the comparison circuit 17 is insulated and transmitted to the control circuit 1 side via the photocoupler FU3, and the PWM signal SD7 that is insulated and transmitted to the control circuit 1 side is not required by the low-pass filter 6. After the high frequency components are removed, they are input to the V _H comparator 4. When the PWM signal SD7 is sent via the photocoupler FU3, the _VH comparator 4 compares the PWM signal SD7 with the step-up / step-down command value SP so that the PWM signal SD7 follows the step-up / step-down command value SP. The gate signal generator 5 can control the duty ratio of the gate drive PWM signals SU1, SD1.

  When the gate drive PWM signals SU1 and SD1 generated by the gate signal generator 5 are isolated and transmitted to the gate drivers 9 and 11 via the photocouplers FU1 and FU2, respectively, the photocouplers FU1 and FU2 Output signals SU2 and SD2 are input to output signal monitoring circuits 21 and 22, respectively. When the output signals SU2 and SD2 from the photocouplers FU1 and FU2 are input to the output signal monitoring circuits 21 and 22, respectively, the output signal monitoring circuits 21 and 22 output the output signals SU2 and SD2 of the photocouplers FU1 and FU2. The signal level is monitored, and the monitoring result is transmitted to the current control circuits 23 and 24 on the control circuit 1 side through the photocouplers FU4 and FU5, respectively.

  When the current control circuits 23 and 24 receive the monitoring results of the signal levels of the output signals SU2 and SD2 of the photocouplers FU1 and FU2 from the output signal monitoring circuits 21 and 22, respectively, the signals on the output side of the photocouplers FU1 and FU2 Based on the level, it is possible to control the forward current of the light emitting diode that flows to the input side of the photocouplers FU1 and FU2.

  Thus, by monitoring the signal level on the output side of the photocouplers FU1 and FU2, the photocoupler FU1 is selected according to the environmental temperature in which the photocouplers FU1 and FU2 are used and the current conversion efficiency of the photocouplers FU1 and FU2. , It becomes possible to control the forward current of the light emitting diode flowing to the input side of FU2. For this reason, as the environmental temperature increases, the forward current of the light emitting diodes on the input side of the photocouplers FU1 and FU2 is reduced, or in the initial operation period in which the current conversion efficiency of the photocouplers FU1 and FU2 is less decreased, the photocoupler FU1. , It is possible to limit the forward current of the light emitting diode on the input side of FU2 to an originally required value, and to suppress the propagation delay of signals by the photocouplers FU1 and FU2, and to shorten the lifetime of the photocouplers FU1 and FU2. It becomes possible to improve.

FIG. 2 is a block diagram showing a schematic configuration of the photocoupler driving device according to the first embodiment of the present invention.
In FIG. 2, the driving device for the photocoupler FC1 is provided with photocouplers FC1 and FC2 that perform insulated transmission of signals between the low pressure side and the high pressure side. Here, the photocoupler FC1 is generated by an infrared light emitting diode PD1 that emits infrared light by a forward current If, a light receiving diode PD2 that receives infrared light emitted from the infrared light emitting diode PD1, and a light receiving diode PD2. A phototransistor M2 that performs a current amplification operation using the photocurrent as a base current is provided. R28 is connected in parallel to the infrared light emitting diode PD1, and the cathode of the infrared light emitting diode PD1 is connected to the field effect transistor M1 through the resistor R29 and the resistor R00 in this order. The collector of the phototransistor M2 is connected to the power supply voltage Vcc2 via the load resistor RL, and the output signal Vout output via the collector of the phototransistor M2 is sent to the IGBT drive IC 30 via the resistor R _LPF. Entered. The resistor R _LPF inserted between the input terminal of the IGBT drive IC 30 and the collector of the phototransistor M2 is for removing minute noise, and the resistor R _LPF is not necessarily inserted.

  In addition, the photocoupler FC2 includes an infrared light emitting diode PD4 that emits infrared light, a light receiving diode PD3 that receives infrared light emitted from the infrared light emitting diode PD4, and a photocurrent generated by the light receiving diode PD3 as a base current. A phototransistor M3 for performing a current amplification operation is provided. R27 is connected in parallel to the infrared light emitting diode PD4, and the cathode of the resistance infrared light emitting diode PD4 is connected to the time interval / PWM pulse conversion circuit. The collector of the phototransistor M2 is connected to the power supply voltage Vcc3 via the resistor R26 and is also connected to the arithmetic unit 36.

  In the driving device for the photocoupler FC1, on the output side of the photocoupler FC1, the operational amplifier 32 that compares the output signal Vout from the photocoupler FC with the reference voltage Vref1, the output signal Vout from the photocoupler FC and the reference voltage It is measured by an operational amplifier 33 for comparing Vref2 and a pulse time interval measuring circuit 31 and a pulse time interval measuring circuit 31 for measuring a time difference when the output signal Vout from the photocoupler FC reaches the reference voltages Vref1 and Vref2, respectively. A time interval / PWM pulse conversion circuit 34 for generating a PWM pulse corresponding to the time difference is provided.

  The signal for measuring the time difference when the reference voltages Vref1 and Vref2 are respectively reached may be any signal on which the photocurrent of the phototransistor M2 constituting the photocoupler FC1 acts. For example, the input terminal of the IGBT drive IC 30 Or a voltage at the collector terminal of the phototransistor M2. Further, the reference voltages Vref1 and Vref2 can be set to different levels in the portion where the falling edge of the output signal Vout from the photocoupler is inclined.

In the driving device for the photocoupler FC1, on the input side of the photocoupler FC1, there is a correspondence relationship between the time difference measured by the pulse time interval measurement circuit 31 and the current Ic-I _LV-IC flowing through the load resistor RL. By referring to the registered time interval / current correspondence table 35 and time interval / current correspondence table 35, the current I _{C_R} −I _{LV−IC_R} actually flowing through the load resistance RL is estimated, and based on the estimation result. An arithmetic unit 36 that increases or decreases the voltage of the variable voltage source 37 and a variable voltage source 37 that varies the forward voltage applied to the light emitting diode PD1 on the input side of the photocoupler FC1 are provided.

When the input signal Vin is input to the gate of the field effect transistor M1, the forward current If flows to the infrared light emitting diode PD1, and infrared light is emitted. The infrared light emitted from the infrared light emitting diode PD1 is received by the light receiving diode PD2, and a photocurrent corresponding to the infrared light flows to the base of the phototransistor M2. When a photocurrent flows to the base of the phototransistor M2, a collector current Ic flows to the phototransistor M2, and a steady current ILV _-IC is discharged from the current mirror circuit in the IGBT drive _{IC 30} to the outside through the resistor R _LPF. Thus, the current flowing through the load resistor RL having one end connected to the power supply voltage Vcc2 is Ic-I _LV-IC . Then, the change in the voltage at the other end of the load resistor RL due to the change in the collector current Ic is input to the IGBT drive IC 30 via the resistor R _LPF as the output signal Vout from the photocoupler FC as shown in the equation (4). The

  Further, the output signal Vout input to the IGBT drive IC 30 is sent to the operational amplifiers 32 and 33, and the level of the output signal Vout is compared with the reference voltages Vref1 and Vref2 by the operational amplifiers 32 and 33, respectively. When the level of the output signal Vout reaches the reference voltages Vref1 and Vref2, the output levels of the operational amplifiers 32 and 33 change from the low level to the high level, respectively, and the time difference when the output levels of the operational amplifiers 32 and 33 change. Is measured by the pulse time interval measuring circuit 31, and the measurement result is sent to the time interval / PWM pulse converting circuit 34.

  When the time difference when the output levels of the operational amplifiers 32 and 33 change is sent to the time interval / PWM pulse conversion circuit 34, the time interval / PWM pulse conversion circuit 34 is measured by the pulse time interval measurement circuit 31. The PWM pulse corresponding to the time difference is generated, and the PWM pulse is applied to the cathode of the infrared light emitting diode PD4. When the PWM pulse generated by the time interval / PWM pulse conversion circuit 34 is applied to the cathode of the infrared light emitting diode PD4, a forward current flows through the infrared light emitting diode PD4 corresponding to the level of the PWM pulse. Infrared light is emitted.

  The infrared light emitted from the infrared light emitting diode PD4 is received by the light receiving diode PD3, and a photocurrent corresponding to the infrared light flows to the base of the phototransistor M3. When a photocurrent flows through the base of the phototransistor M3, a collector current flows through the phototransistor M3, and the collector current flows into a resistor R26 having one end connected to the power supply voltage Vcc3. Then, the time difference measured by the pulse time interval measuring circuit 31 is input to the arithmetic unit 36 as a change in the other end voltage of the resistor R26 accompanying a change in the collector current flowing through the phototransistor M3.

Then, when the time difference measured by the pulse time interval measurement circuit 31 is input, the arithmetic unit 36 refers to the time interval / current correspondence table 35 so that the current I _{C_R} actually flowing in the load resistance RL is _obtained. -I _{LV-IC_R} is estimated and a known value is applied as I _{LV- IC_R} to calculate the collector current I _{C_R} actually flowing through the phototransistor M2. Then, the arithmetic unit 36, the collector current I _{C_R} that actually flows through the phototransistor M2, compared with the predefined collector current I _{C_S} to flow to the photo transistor M2, are actually flowing in the phototransistor M2 The collector current I _{C — R} flows through the light emitting diode PD1 on the input side of the photocoupler FC1 while increasing or decreasing the voltage of the variable voltage source 37 so that the collector current I _{C — S} matches the collector current I _{C — S} defined in advance so as to flow through the phototransistor M2. The forward current If can be controlled.

When the voltage value of the variable voltage source 37 exceeds a value corresponding to the allowable pulse current of the light emitting diode PD1 of the photocoupler FC1, the arithmetic unit 36 determines that the photocoupler FC1 has reached the life limit. The alarm signal AL is generated.
As the arithmetic unit 36, for example, a CPU that executes a program in which the above-described method for controlling the forward current If can be used. Further, since the gate drive signal of the IGBT is several kHz to several tens kHz, the above-described forward current If can be frequently controlled.

  As a result, the slope of the falling edge of the output signal Vout of the photocoupler FC1 is calculated on the output side of the photocoupler FC1, thereby referring to the signal on the input side of the photocoupler FC1 (the forward current If flowing in the infrared light emitting diode PD1). The forward current If of the light-emitting diode PD1 flowing on the input side of the photocoupler FC1 can be controlled according to the environmental temperature in which the photocoupler FC1 is used and the deterioration of the current conversion efficiency of the photocoupler FC1. Become. For this reason, it is possible to improve the life of the photocoupler FC1 while suppressing the propagation delay of the signal by the photocoupler FC1, even when the signal is insulated and transmitted between the low voltage side and the high voltage side. In addition, even when the current conversion efficiency of the photocoupler FC1 decreases, the value of the current flowing through the load resistor RL can be kept constant, and an increase in signal propagation delay due to the photocoupler FC1 can be suppressed.

FIG. 3 is a block diagram showing a schematic configuration of the IGBT drive IC of FIG.
3, the IGBT drive IC 30 includes a pull-up function of the input terminal of the IGBT drive IC 30, a binarization function of the output signal Vout from the photocoupler FC1, a gate drive function of the IGBT, and an overcurrent / overtemperature protection function of the IGBT. Is provided.
That is, the IGBT drive _IC 30 includes a current source 41 including a current mirror circuit for discharging the steady current I _LV-IC to the outside, a binarization circuit 42 for binarizing the output signal Vout from the photocoupler FC1, A MOS-FET driver 44 for performing IGBT gate drive, logic circuits 43 and 45 for performing overcurrent / overtemperature protection of the IGBT, a temperature signal comparator 46, and a current signal comparator 47 are provided.

When a PWM signal is input to the IGBT drive _{IC 30} while discharging the steady current I _LV-IC generated by the current source 41 to the outside, the binarization circuit 42 binarizes the PWM signal. 43 is supplied to the MOS-FET driver 44 through 43, and the gate drive of the IGBT is performed.
In addition, when the IGBT temperature signal is input to the temperature signal comparator 46 and the IGBT current signal is input to the current signal comparator 47 and the threshold value that the IGBT does not break is exceeded, an alarm signal is sent via the logic circuit 45. And the generation of the gate signal by the logic circuit 43 is stopped, whereby the current flowing through the IGBT can be cut off and the IGBT can be protected from destruction.

Here, in order to set the output of the IGBT drive IC 30 in FIG. 2 to the low level, when the forward current If flowing through the infrared light emitting diode PD1 is set to 0, in the equation (4), Vout = Vcc2 + R _LPF × I _LV-IC The output signal Vout from the photocoupler FC is always a voltage higher than VINH.
On the other hand, in order to set the output of the IGBT drive IC 30 to a high level, the current conversion efficiency of the photocoupler FC needs to consider the deterioration life in addition to the variation of circuit elements, temperature characteristics, and fluctuations in the power supply voltage. It is necessary to flow the forward current If so as to satisfy the condition of Vout ≦ VINL at an operation guaranteed temperature of −30 ° C. at which the current conversion efficiency of the photocoupler FC is the lowest when the environment is 100 ° C. and the operation time is 15000 hours.

  Then, the power supply voltage Vcc2 is set to 5V, 8V, so as to satisfy the condition of Vout ≦ VINL at the operation guarantee temperature of −30 ° C. at which the current conversion efficiency of the photocoupler FC is the lowest in the operation environment of 100 ° C. and the operation time of 15000 hours. When the value of the load resistance RL when it is generated by an 11V tuner diode is obtained, RL ≧ 16.2 kΩ for a power supply voltage Vcc2 of 11V, and RL ≧ 11.3 kΩ for a tuner diode of 8V power supply voltage Vcc2. In the case of a tuner diode with a power supply voltage Vcc2 of 5 V, the IGBT drive IC 30 can operate reliably until the product lifetime when RL ≧ 6.8 kΩ.

  As shown in FIG. 20, the dead times DT1 and DT2 are normally set to about 5 μs so that the upper arm 2 and the lower arm 3 of FIG. 1 are not short-circuited. It is not desirable that the dead times DT1 and DT2 become narrow during transmission, and the difference ΔT between the fall time TPHL and the rise time TpLH of the output signal Vout in FIG. 18 should be as small as possible. When the input of the IGBT drive IC 30 becomes a low level, the IGBT is turned on. Therefore, when TPHL ≧ TpLH, the dead times DT1 and DT2 increase, and when TpHL ≦ TpLH, the dead times DT1 and DT2 decrease. To do. The difference ΔT between the fall time TPHL and the rise time TpLH of the output signal Vout is the entire operating temperature range from −30 ° C. to + 100 ° C. in consideration of the propagation time difference in the IGBT drive IC 30 and the IGBT switching time difference. It is preferable to suppress to at least 2 μs or less.

  4A shows the rising waveform of the input-side voltage Vin and the falling waveform of the output-side voltage Vout in the initial state of the photocoupler of FIG. 2, and FIG. 4B shows the initial state of the photocoupler of FIG. 4C shows the rising waveform of the input-side voltage Vin and the rising waveform of the output-side voltage Vout. FIG. 4C shows the rising waveform of the input-side voltage Vin and the output-side voltage when the photocoupler of FIG. FIG. 4D shows the falling waveform of the input side voltage Vin and the rising waveform of the output side voltage Vout in the life deterioration state of the photocoupler of FIG.

  In FIG. 4, in the life deterioration state of the photocoupler FC1, there is almost no change in the rising slope of the output voltage Vout compared to the initial state of the photocoupler FC1, whereas the falling of the output voltage Vout The inclination becomes smaller. Therefore, by monitoring the falling slope of the output voltage Vout from the photocoupler FC1, the life deterioration state of the photocoupler FC1 can be determined.

  When the life of the photocoupler FC1 is deteriorated, the collector current Ic flowing through the phototransistor M2 is reduced as shown in the equation (2). Therefore, the collector current Ic flowing through the phototransistor M2 is monitored, and the phototransistor M2 is monitored. By controlling the forward current If flowing through the light emitting diode PD1 so that the flowing collector current Ic becomes constant, an increase in signal propagation delay by the photocoupler FC1 can be suppressed.

FIG. 5 is a diagram illustrating the relationship between the current conversion efficiency of the photocoupler according to an embodiment of the present invention and the fall time TpLH of the output-side voltage Vout as a parameter, and FIG. 6 illustrates the embodiment of the present invention. It is a figure which shows temperature as a parameter about the relationship between the current conversion efficiency of the photocoupler which concerns, and the rise time TPHL of the voltage Vout on the output side.
5 and 6, the delay time TpLH of the rising waveform by the photocoupler FC1 is less dependent on the current conversion efficiency of the photocoupler FC1, whereas the delay time TPHL of the falling waveform by the photocoupler FC1 is The current conversion efficiency of the coupler FC1 increases as it deteriorates, and this tendency is particularly noticeable as the temperature decreases.

  Therefore, by monitoring the falling slope of the output voltage Vout from the photocoupler FC1, it is possible to determine the life deterioration state of the photocoupler FC1, and to emit light so that the collector current Ic flowing through the phototransistor M2 becomes constant. By controlling the forward current If flowing in the diode PD1, the delay time TPHL of the signal by the photocoupler FC1 is kept constant regardless of the environmental temperature in which the photocoupler FC1 is used and the deterioration of the current conversion efficiency of the photocoupler FC1. Can do.

FIG. 7 is a cross-sectional view showing a schematic configuration of an intelligent power module for a buck-boost converter according to an embodiment of the present invention.
In FIG. 7, in the step-up / down converter intelligent power module, the drive circuit 105 is mounted on the upper stage of the circuit board 104, and the IGBT chip 103 is mounted on the lower stage of the circuit board 104. The circuit board 104 on which the IGBT chip 103 and the drive circuit 105 are mounted is accommodated in the case 101, and the main circuit terminal 108 is taken out through the case 101 and attached to the cooling fin 107 through the heat dissipation base 102. ing.

  During operation of the intelligent power module for the buck-boost converter, the circuit board 104 is cooled by generating heat from the IGBT chip 103 due to the switching loss of the IGBT and flowing cooling water through the cooling fins 107. Here, during the continuous operation of the intelligent power module for the step-down converter, the temperature of the cooling water becomes 70 to 80 ° C., so the temperature of the circuit board 104 rises to around 100 ° C. Therefore, the output signal Vout around 100 ° C. It is preferable to design the circuit in consideration of the difference ΔT between the fall time TPHL and the rise time TpLH.

  Here, when designing the circuit of the intelligent power module for the buck-boost converter, the condition that the difference ΔT between the fall time TPHL and the rise time TpLH of the output signal Vout when insulated transmission is performed via the photocoupler FC1 is 2 μs or less. After reaching the end of the CTR life that has been used under the strictest conditions of the specified temperature range, circuit constants that satisfy the threshold value of the subsequent circuit even at the temperature with the lowest current conversion efficiency of the photocoupler FC1 are adopted. It is preferable to do.

  FIG. 8A is a diagram showing the temperature dependence of the fall time TPHL in the initial state of the photocoupler when the load resistance is a parameter, and FIG. 8B is a photocoupler when the load resistance is a parameter. FIG. 8C shows the temperature dependence of the rise time TPHL in the initial state, and FIG. 8C shows the temperature of the difference ΔT between the fall time TPLL and the rise time TpLH in the initial state of the photocoupler when the load resistance is a parameter. FIG. 8D is a diagram showing the temperature dependence of the fall time TpHL after 15000 hours of life deterioration of the photocoupler when the load resistance is used as a parameter (CTR = 9.5%). FIG. 8 (e) shows the rise time after deterioration of the lifetime of the photocoupler when the load resistance is a parameter (CTR = 9.5%). FIG. 8 (f) shows the temperature dependence of pHL. The fall time TpHL and the rise time TpLH after 15000-hour life deterioration of the photocoupler (CTR = 9.5%) when the load resistance is used as a parameter are shown in FIG. It is a figure which shows the temperature dependence of difference (DELTA) T.

In the example of FIG. 8, the power supply voltage Vcc2 applied to the load resistor RL in FIG. 2 is 5 V, the actual value of the photocoupler in the initial state, and the CTR value at −30 ° C. is 9.5%. In comparison with the worst value after 15000 hours of continuous use in an environment of 100 ° C.
In FIG. 8, in order for the IGBT drive IC 30 to operate within the entire operating temperature range from −30 ° C. to + 100 ° C. at the power supply voltage Vcc2 of 11 V, the value of the load resistance RL must be 16.2 kΩ or more. The difference ΔT between the fall time TPHL and the rise time TpLH of the output signal Vout does not exceed 2 μs or less at the actual value of the initial state of the photocoupler at + 100 ° C. Accordingly, the dead times DT1 and DT2 of FIG. 21 are narrow during signal transmission by the photocoupler FC of FIG. 2 from the start of use of the photocoupler until the lapse of 15000 hours within the entire use temperature range from −30 ° C. to + 100 ° C. Can be prevented.

FIG. 9 is a block diagram showing a schematic configuration of a photocoupler driving device according to the second embodiment of the present invention.
In FIG. 9, on the input side of the photocoupler FC1, instead of the arithmetic unit 36 and the time interval / current correspondence table 35 of FIG. 2, an operational amplifier 38 for comparing the output signal from the phototransistor M3 with the reference voltage Vref4, photo A resistor R25 for inputting an output signal from the transistor M3 to the inverting input terminal of the operational amplifier 38 and a capacitor C1 connected between the inverting input terminal and the output terminal of the operational amplifier 38 are provided, and the voltage of the variable voltage source 37 is provided. Is provided with an operational amplifier 39 for comparing the signal with the reference voltage Vref3.

The time difference measured by the pulse time interval measurement circuit 31 is input to the operational amplifier 38 via the resistor R25 as a change in the other end voltage of the resistor R26 accompanying a change in the collector current flowing through the phototransistor M3.
When the output signal from the phototransistor M3 is input, the operational amplifier 38 compares the level of the output signal with the reference voltage Vref4, and calculates the difference between the level of the output signal from the phototransistor M3 and the reference voltage Vref4. The voltage output from the phototransistor M3 to the light emitting diode PD1 on the input side of the photocoupler FC1 while increasing or decreasing the voltage of the variable voltage source 37 so that the level of the output signal from the phototransistor M3 matches the reference voltage Vref4. By controlling the flowing forward current If, the value of the current flowing through the load resistor RL can be kept constant.

  The voltage of the variable voltage source 37 is applied to the light emitting diode PD1 and also input to the operational amplifier 38. When the voltage value of the variable voltage source 37 exceeds the reference voltage Vref3, the operational amplifier 38 determines that the photocoupler FC1 has reached the life limit and generates an alarm signal AL. The reference voltage Vref3 can be set to a value corresponding to the allowable pulse current of the light emitting diode PD1 of the photocoupler FC1.

FIG. 10 is a block diagram showing a schematic configuration of a photocoupler driving device according to the third embodiment of the present invention.
In FIG. 10, the output signal Vout from the photocoupler FC is connected to the output side of the photocoupler FC1 instead of the operational amplifiers 32 and 33, the pulse time interval measurement circuit 31 and the time interval / PWM pulse conversion circuit 34 in FIG. An operational amplifier 51 that compares the reference voltage Vref is provided.
Further, on the input side of the photocoupler FC1, instead of the arithmetic unit 36 and the time interval / current correspondence table 35 in FIG. 2, the time from when the input signal Vin is input until the output signal of the phototransistor M3 is input. A counter 52 that counts the interval, a count value / current correspondence table 53, and a count value / current correspondence table 53 in which the correspondence between the count value by the counter 52 and the current Ic-I _LV-IC flowing through the load resistor RL is registered. By referring to the calculation unit 54, the current I _{C — R} −I _{LV −IC_R} actually flowing in the load resistor RL is estimated, and the voltage of the variable voltage source 37 is increased or decreased based on the estimation result.

When the input signal Vin is input to the gate of the field effect transistor M1, the forward current If flows to the infrared light emitting diode PD1, and infrared light is emitted. The infrared light emitted from the infrared light emitting diode PD1 is received by the light receiving diode PD2, and a photocurrent corresponding to the infrared light flows to the base of the phototransistor M2. When a photocurrent flows to the base of the phototransistor M2, a collector current Ic flows to the phototransistor M2, and a steady current ILV _-IC is discharged from the current mirror circuit in the IGBT drive _{IC 30} to the outside through the resistor R _LPF. Thus, the current flowing through the load resistor RL having one end connected to the power supply voltage Vcc2 is Ic-I _LV-IC . Then, the change in the voltage at the other end of the load resistor RL due to the change in the collector current Ic is input to the IGBT drive IC 30 via the resistor R _LPF as the output signal Vout from the photocoupler FC as shown in the equation (4). The

The input signal Vin is input to the gate of the field effect transistor M1 and also to the counter 52. When the input signal Vin is input to the counter 52, the counter 52 starts counting.
The output signal Vout input to the IGBT drive IC 30 is sent to the operational amplifier 51, and the output signal Vout is compared with the reference voltage Vref by the operational amplifier 51. When the level of the output signal Vout reaches the reference voltage Vref, the output level of the operational amplifier 51 changes from the low level to the high level, and the output level of the operational amplifier 51 is applied to the cathode of the infrared light emitting diode PD4. When the output level of the operational amplifier 51 is applied to the cathode of the infrared light emitting diode PD4, a forward current flows through the infrared light emitting diode PD4 corresponding to the output level of the operational amplifier 51, and infrared light is emitted. .

The infrared light emitted from the infrared light emitting diode PD4 is received by the light receiving diode PD3, and a photocurrent corresponding to the infrared light flows to the base of the phototransistor M3. When a photocurrent flows through the base of the phototransistor M3, a collector current flows through the phototransistor M3, and the collector current flows into a resistor R26 having one end connected to the power supply voltage Vcc3. A change in the output level of the operational amplifier 51 is input to the counter 52 as a change in the voltage at the other end of the resistor R26 accompanying a change in the collector current flowing through the phototransistor M3.
When the change in the output level of the operational amplifier 51 is input, the counter 52 stops the count operation, and calculates the count value from when the input signal Vin is input until the output level of the operational amplifier 51 changes. 54.

When the arithmetic unit 54 receives the count value from the counter 52, the arithmetic unit 54 estimates the current I _{C_R} −I _{LV−IC_R} actually flowing through the load resistance RL by referring to the count value / current correspondence table 53. By applying a known value as I _{LV-IC_R} , the collector current I _{C_R} actually flowing through the phototransistor M2 is calculated. Then, the arithmetic unit 54, the collector current I _{C_R} that actually flows through the phototransistor M2, compared with the predefined collector current I _{C_S} to flow to the photo transistor M2, are actually flowing in the phototransistor M2 The collector current I _{C — R} flows through the light emitting diode PD1 on the input side of the photocoupler FC1 while increasing or decreasing the voltage of the variable voltage source 37 so that the collector current I _{C — S} matches the collector current I _{C — S} defined in advance so as to flow through the phototransistor M2. The forward current If can be controlled.
When the voltage value of the variable voltage source 37 exceeds a value corresponding to the allowable pulse current of the light emitting diode PD1 of the photocoupler FC1, the arithmetic unit 54 determines that the photocoupler FC1 has reached the life limit. The alarm signal AL can be generated.

FIG. 11 is a block diagram showing a schematic configuration of a photocoupler driving device according to the fourth embodiment of the present invention.
In FIG. 11, the driving device for the photocoupler FC1 is provided with photocouplers FC1 and FC2 that perform insulated transmission of signals between the low pressure side and the high pressure side. Here, the photocoupler FC1 is generated by an infrared light emitting diode PD1 that emits infrared light by a forward current If, a light receiving diode PD2 that receives infrared light emitted from the infrared light emitting diode PD1, and a light receiving diode PD2. A phototransistor M2 that performs a current amplification operation using the photocurrent as a base current is provided. R28 is connected in parallel to the infrared light emitting diode PD1, and the cathode of the infrared light emitting diode PD1 is connected to the field effect transistor M1 through the resistor R29 and the resistor R00 in this order. The collector of the phototransistor M2 is connected to the power supply voltage Vcc2, the emitter of the phototransistor M2 is connected to the ground potential through the resistor RL, and the output signal Vout output through the emitter of the phototransistor M2 is It is input to the IGBT drive IC 30 via the resistor R _LPF . The resistor R _LPF inserted between the input terminal of the IGBT drive IC 30 and the emitter of the phototransistor M2 is for removing minute noise, and the resistor R _LPF is not necessarily inserted.

  In addition, the photocoupler FC2 includes an infrared light emitting diode PD4 that emits infrared light, a light receiving diode PD3 that receives infrared light emitted from the infrared light emitting diode PD4, and a photocurrent generated by the light receiving diode PD3 as a base current. A phototransistor M3 for performing a current amplification operation is provided. R27 is connected in parallel to the infrared light emitting diode PD4, and the cathode of the resistance infrared light emitting diode PD4 is connected to the time interval / PWM pulse conversion circuit. The collector of the phototransistor M2 is connected to the power supply voltage Vcc3 via the resistor R26 and is also connected to the arithmetic unit 36.

  In the driving device for the photocoupler FC1, on the output side of the photocoupler FC1, the operational amplifier 132 that compares the output signal Vout from the photocoupler FC with the reference voltage Vref1, the output signal Vout from the photocoupler FC and the reference voltage It is measured by an operational amplifier 133 that compares with Vref2, a pulse time interval measuring circuit 131 that measures a time difference when the output signal Vout from the photocoupler FC reaches the reference voltages Vref1 and Vref2, and a pulse time interval measuring circuit 131, respectively. A time interval / PWM pulse conversion circuit 134 for generating a PWM pulse corresponding to the time difference is provided.

  The signal for measuring the time difference when the reference voltages Vref1 and Vref2 are respectively reached may be any signal on which the photocurrent of the phototransistor M2 constituting the photocoupler FC1 acts. For example, the input terminal of the IGBT drive IC 30 May be a signal (output signal Vout) that is input to, or a voltage at the emitter terminal of the phototransistor M2. Further, the reference voltages Vref1 and Vref2 can be set to different levels in the portion where the rising edge of the output signal Vout from the photocoupler is inclined.

In the driving device for the photocoupler FC1, on the input side of the photocoupler FC1, there is a correspondence relationship between the time difference measured by the pulse time interval measurement circuit 131 and the current Ic-I _LV-IC flowing through the load resistor RL. By referring to the registered time interval / current correspondence table 135 and time interval / current correspondence table 135, the current I _{C_R} −I _{LV−IC_R} actually flowing through the load resistance RL is estimated, and based on the estimation result An arithmetic unit 136 that increases or decreases the voltage of the variable voltage source 37 and a variable voltage source 137 that varies the forward voltage applied to the light emitting diode PD1 on the input side of the photocoupler FC1 are provided.

When the input signal Vin is input to the gate of the field effect transistor M1, the forward current If flows to the infrared light emitting diode PD1, and infrared light is emitted. The infrared light emitted from the infrared light emitting diode PD1 is received by the light receiving diode PD2, and a photocurrent corresponding to the infrared light flows to the base of the phototransistor M2. When a photocurrent flows through the base of the phototransistor M2, a collector current Ic flows through the phototransistor M2, and a steady current ILV _-IC is sucked into the current mirror circuit in the IGBT drive _{IC 30} from the outside via the resistor R _LPF. Thus, the current flowing through the load resistor RL having one end connected to the ground potential is Ic-I _LV-IC . Then, the change in the voltage at the other end of the load resistor RL accompanying the change in the collector current Ic is input to the IGBT drive IC 30 via the resistor R _LPF as the output signal Vout from the photocoupler FC.

  Further, the output signal Vout input to the IGBT drive IC 30 is sent to the operational amplifiers 132 and 133, and the level of the output signal Vout is compared with the reference voltages Vref1 and Vref2 by the operational amplifiers 132 and 133, respectively. When the level of the output signal Vout reaches the reference voltages Vref1 and Vref2, the output levels of the operational amplifiers 132 and 133 change from low level to high level, respectively, and the time difference when the output levels of the operational amplifiers 132 and 133 change. Is measured by the pulse time interval measurement circuit 131, and the measurement result is sent to the time interval / PWM pulse conversion circuit 134.

  When the time difference when the output levels of the operational amplifiers 132 and 133 change is sent to the time interval / PWM pulse conversion circuit 134, the time interval / PWM pulse conversion circuit 134 is measured by the pulse time interval measurement circuit 131. The PWM pulse corresponding to the time difference is generated, and the PWM pulse is applied to the cathode of the infrared light emitting diode PD4. When the PWM pulse generated by the time interval / PWM pulse conversion circuit 134 is applied to the cathode of the infrared light emitting diode PD4, a forward current flows through the infrared light emitting diode PD4 corresponding to the level of the PWM pulse. Infrared light is emitted.

  The infrared light emitted from the infrared light emitting diode PD4 is received by the light receiving diode PD3, and a photocurrent corresponding to the infrared light flows to the base of the phototransistor M3. When a photocurrent flows through the base of the phototransistor M3, a collector current flows through the phototransistor M3, and the collector current flows into a resistor R26 having one end connected to the power supply voltage Vcc3. Then, the time difference measured by the pulse time interval measurement circuit 131 is input to the arithmetic unit 136 as a change in the other end voltage of the resistor R26 accompanying a change in the collector current flowing through the phototransistor M3.

Then, when the time difference measured by the pulse time interval measurement circuit 131 is input, the arithmetic unit 136 refers to the time interval / current correspondence table 135 to thereby refer to the current I _{C_R} actually flowing through the load resistor RL. -I _{LV-IC_R} is estimated and a known value is applied as I _{LV- IC_R} to calculate the collector current I _{C_R} actually flowing through the phototransistor M2. Then, the arithmetic unit 136, the collector current I _{C_R} that actually flows through the phototransistor M2, compared with the predefined collector current I _{C_S} to flow to the photo transistor M2, are actually flowing in the phototransistor M2 The collector current I _{C — R} flows through the light emitting diode PD1 on the input side of the photocoupler FC1 while increasing or decreasing the voltage of the variable voltage source 37 so that the collector current I _{C — S} matches the collector current I _{C — S} defined in advance so as to flow through the phototransistor M2. The forward current If can be controlled.

When the voltage value of the variable voltage source 37 exceeds a value corresponding to the allowable pulse current of the light emitting diode PD1 of the photocoupler FC1, the arithmetic unit 136 determines that the photocoupler FC1 has reached the life limit. The alarm signal AL is generated.
Thus, the slope of the rising edge of the output signal Vout of the photocoupler FC1 is calculated on the output side of the photocoupler FC1, thereby referring to the signal on the input side of the photocoupler FC1 (the forward current If flowing in the infrared light emitting diode PD1). The forward current If of the light emitting diode PD1 flowing on the input side of the photocoupler FC1 can be controlled according to the environmental temperature in which the photocoupler FC1 is used and the deterioration of the current conversion efficiency of the photocoupler FC1. . For this reason, it is possible to improve the life of the photocoupler FC1 while suppressing the propagation delay of the signal by the photocoupler FC1, even when the signal is insulated and transmitted between the low voltage side and the high voltage side. In addition, even when the current conversion efficiency of the photocoupler FC1 decreases, the value of the current flowing through the load resistor RL can be kept constant, and an increase in signal propagation delay due to the photocoupler FC1 can be suppressed.

1 is a block diagram illustrating a schematic configuration of an intelligent power module for a buck-boost converter to which a photocoupler driving device according to an embodiment of the present invention is applied. 1 is a block diagram showing a schematic configuration of a photocoupler driving device according to a first embodiment of the present invention. FIG. 3 is a block diagram showing a schematic configuration of the IGBT drive IC of FIG. 2. 4A shows the rising waveform of the input-side voltage Vin and the falling waveform of the output-side voltage Vout in the initial state of the photocoupler of FIG. 2, and FIG. 4B shows the initial state of the photocoupler of FIG. 4C shows the rising waveform of the input-side voltage Vin and the rising waveform of the output-side voltage Vout. FIG. 4C shows the rising waveform of the input-side voltage Vin and the output-side voltage when the photocoupler of FIG. FIG. 4D shows the falling waveform of the input side voltage Vin and the rising waveform of the output side voltage Vout in the life deterioration state of the photocoupler of FIG. It is a figure which shows temperature as a parameter about the relationship between the current conversion efficiency of the photocoupler which concerns on one Embodiment of this invention, and fall time TpLH of the voltage Vout on the output side. It is a figure which shows temperature as a parameter about the relationship between the current conversion efficiency of the photocoupler which concerns on one Embodiment of this invention, and the rise time TPHL of the voltage Vout on the output side. It is sectional drawing which shows schematic structure of the intelligent power module for buck-boost converters concerning one embodiment of this invention. FIG. 8A is a diagram showing the temperature dependence of the fall time TPHL in the initial state of the photocoupler when the load resistance is a parameter, and FIG. 8B is a photocoupler when the load resistance is a parameter. FIG. 8C shows the temperature dependence of the rise time TPHL in the initial state, and FIG. 8C shows the temperature of the difference ΔT between the fall time TPLL and the rise time TpLH in the initial state of the photocoupler when the load resistance is a parameter. FIG. 8D is a diagram showing the temperature dependence of the fall time TpHL after 15000 hours of life deterioration of the photocoupler when the load resistance is used as a parameter (CTR = 9.5%). FIG. 8 (e) shows the rise time after deterioration of the lifetime of the photocoupler when the load resistance is a parameter (CTR = 9.5%). FIG. 8 (f) shows the temperature dependence of pHL. The fall time TpHL and the rise time TpLH after 15000-hour life deterioration of the photocoupler (CTR = 9.5%) when the load resistance is used as a parameter are shown in FIG. It is a figure which shows the temperature dependence of difference (DELTA) T. It is a block diagram which shows schematic structure of the drive device of the photocoupler which concerns on 2nd Embodiment of this invention. It is a block diagram which shows schematic structure of the drive device of the photocoupler which concerns on 3rd Embodiment of this invention. It is a block diagram which shows schematic structure of the drive device of the photocoupler which concerns on 4th Embodiment of this invention. It is a block diagram which shows schematic structure of the vehicle drive system using the conventional buck-boost converter. It is a block diagram which shows schematic structure of the buck-boost converter of FIG. It is a figure which shows the waveform of the electric current which flows into the reactor of FIG. 13 at the time of pressure | voltage rise operation. It is a figure which shows the structure of the transmission circuit of the PWM signal using a photocoupler. It is a figure which shows the collector / emitter voltage dependence of the current conversion efficiency when the forward current If which flows into the light emitting diode of a photocoupler at 20 degreeC is made into a parameter. It is a figure which shows the temperature dependence of the current conversion efficiency when using the collector current Ic of the phototransistor with respect to the forward current If which flows into the light emitting diode of a photocoupler as a parameter. It is a figure which shows the time-dependent characteristic of the current conversion efficiency when the forward current If which flows into the light emitting diode of a photocoupler is used as a parameter. It is a figure which shows the definition of the propagation delay time of the input signal and output signal in the transmission circuit of the PWM signal using a photocoupler. 20A is a diagram illustrating the propagation delay time characteristic of the photocoupler with respect to the load resistance RL, and FIG. 20B is a diagram illustrating the propagation delay time characteristic of the photocoupler with respect to the ambient temperature Ta. It is a figure which shows the setting method of the dead time of the gate signal of IGBT. It is a figure which shows the temperature dependence of the forward voltage of a light emitting diode. It is a figure which shows the temperature dependence of the on-resistance of a field effect transistor. It is a figure which shows the temperature dependence of the forward current which flows into a light emitting diode. It is a figure which shows the estimated lifetime with respect to the ambient temperature of a photocoupler when a forward direction current is made into a parameter.

Explanation of symbols

SWU, SWD Switching element 1 Control circuit 2 Upper arm 3 Lower arm 4 V _H comparator 5 Gate signal generator 6 Low-pass filter 7, 8 IGBT
9, 11 Gate driver 10, 12 IGBT protection circuit 13 V _H detection circuit 14 Triangular wave generator 15 Level adjustment unit 16 Voltage division circuit 17 Comparison circuit 21, 22 Output signal monitoring circuit 23, 24 Current control circuit FU1 to FU5, FC1, FC2 Photocoupler DU1, DU2, DD1, DD2 Diode RU1, RU2, RD1, RD2, R00, R25, R26, R27, R28, R29, RL, R _LPF resistance M1 Field effect transistor M2, M3 Phototransistor C1 Capacitor 30 IGBT Drive IC
32, 33, 38, 39, 51, 132, 133 Operational amplifier Vref, Vref1, Vref2, Vref3, Vref4 Reference voltage 31, 131 Pulse time interval measurement circuit 34, 134 Time interval / PWM pulse conversion circuit 35, 135 Time interval / Current correspondence table 36, 54, 136 Arithmetic unit 37 Variable voltage source 41 Current source 42 Binary circuit 43, 45 Logic circuit 44 MOS-FET driver 46 Temperature signal comparator 47 Current signal comparator 52 Counter 53 Count value / Current correspondence Table 101 Case 102 Heat radiation base 103 IGBT chip 104 Circuit board 105 Drive circuit 107 Cooling fin 108 Main circuit terminal

Claims (9)

Output signal monitoring means for monitoring the signal level on the output side of the photocoupler;
A driving device for a photocoupler, comprising: current control means for controlling a forward current of a light emitting diode flowing on the input side of the photocoupler based on a signal level monitored by the output signal monitoring means. Inclination detecting means for detecting the rising or falling inclination of the signal on the output side of the photocoupler on the output side of the photocoupler;
Current control means for controlling the forward current of the light emitting diode flowing on the input side of the photocoupler based on the rise or fall slope of the signal on the output side of the photocoupler detected by the slope detection means. A drive device for a photocoupler characterized by the above. The inclination detecting means includes
Level detection means for detecting whether the signal on the output side of the photocoupler has reached a plurality of thresholds of different levels;
A time interval measuring means for measuring a time difference when the signal on the output side of the photocoupler reaches a plurality of threshold values of different levels;
The current control means controls a forward current of the light emitting diode flowing on the input side of the photocoupler based on a time difference when the signal on the output side of the photocoupler reaches a plurality of threshold values having different levels. The photocoupler driving device according to claim 2. A delay time calculating means for detecting a delay time at the time of rising or falling of the signal on the output side of the photocoupler;
Current control means for controlling the forward current of the light emitting diode flowing to the input side of the photocoupler based on the delay time at the rise or fall of the signal on the output side of the photocoupler calculated by the delay time calculation means And a photocoupler driving device.   5. The photocoupler driving device according to claim 1, wherein the signal on the output side of the photocoupler is a signal on which a photocurrent of a phototransistor constituting the photocoupler acts. A variable voltage source that varies a forward voltage applied to the light emitting diode on the input side of the photocoupler;
6. The current control unit according to claim 1, wherein the current control unit controls a forward current of the light emitting diode flowing on an input side of the photocoupler by controlling a voltage of the variable voltage source. The drive device of the described photocoupler.   7. The photocoupler driving device according to claim 6, wherein an alarm is generated when a voltage value of the variable voltage source exceeds a value corresponding to an allowable pulse current of a light emitting diode of the photocoupler. A pair of switching elements connected in series so as to operate for the upper arm and the lower arm, respectively, for energizing and interrupting the current flowing into the load;
A control circuit for generating a control signal instructing conduction and non-conduction of the switching element;
A drive circuit for driving a control terminal of the switching element based on the control signal;
A photocoupler that is provided for each of the switching elements so that the control circuit and the drive circuit are insulated, and that transmits a signal between the control circuit and the drive circuit;
Level detection means for detecting whether the signal on the output side of the photocoupler has reached a plurality of thresholds of different levels;
A time interval measuring means for measuring a time difference when the signal on the output side of the photocoupler reaches a plurality of threshold values of different levels;
Current control means for controlling the forward current of the light emitting diode flowing on the input side of the photocoupler based on the time difference when the signal on the output side of the photocoupler reaches a plurality of threshold values of different levels. The power converter characterized by the above-mentioned. Measuring the time difference when the signal on the output side of the photocoupler reaches a plurality of thresholds of different levels;
Controlling a forward current of a light emitting diode flowing on the input side of the photocoupler based on a time difference when the signal on the output side of the photocoupler reaches a plurality of threshold values of different levels. A photocoupler driving method characterized by the above.

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