阅读说明：本技术 半导体集成电路 (Semiconductor integrated circuit having a plurality of transistors ) 是由 小滨考德 于 2020-02-03 设计创作，主要内容包括：本发明提供在点火器导通时即使电池侧的开关被切断也不使除开关控制下的点火器外的其他电路破损的半导体集成电路。感测IGBT(12)和电流检测电阻Rsns监视主IGBT(11)的集电极电流Ic,若检测到电压因开关切断而降低则迟滞比较器CMP输出电压Vcmp。逻辑电路(15)根据来自输入识别电路(16)的输入识别电压Vin1和电压而输出逻辑输出电压Vlogic。逻辑输出电压导通半导体开关(M1)而降低栅极电压Vgate,导通半导体开关(M2)而降低钳位二极管(D1a、D1b)的耐压。利用钳位二极管(D1a)对因降低栅极电压Vgate而上升的集电极电压Vc进行钳位,防止产生使其他电路破损的异常电压。(The invention provides a semiconductor integrated circuit which does not damage other circuits except an igniter under switch control even if a switch on a battery side is cut off when the igniter is turned on. The sense IGBT (12) and the current detection resistor Rsns monitor the collector current Ic of the main IGBT (11), and when it is detected that the voltage has decreased due to the switch being turned off, the hysteresis comparator CMP outputs a voltage Vcmp. The logic circuit (15) outputs a logic output voltage Vlogic based on the input identification voltage Vin1 and the voltage from the input identification circuit (16). The logic output voltage turns on the semiconductor switch (M1) to lower the gate voltage Vgate, and turns on the semiconductor switch (M2) to lower the withstand voltage of the clamping diodes (D1a, D1 b). The collector voltage Vc increased by lowering the gate voltage Vgate is clamped by a clamping diode (D1a) to prevent the generation of abnormal voltage which damages other circuits.)

1. A semiconductor integrated circuit is provided with:

a semiconductor power switching element that drives an inductive load;

a load current detection circuit that detects a load current of the inductive load;

a logic circuit that outputs a logic signal when the load current detection circuit detects a decrease in the load current while the semiconductor power switching element is on-controlled;

a gate voltage pull-down circuit that pulls down a gate voltage of the semiconductor power switching element if the logic signal is received; and

and a clamp withstand voltage lowering circuit that switches a withstand voltage of a clamp diode provided between a gate of the semiconductor power switching element and a high potential terminal of the semiconductor power switching element to which the inductive load is connected to a low withstand voltage, upon receiving the logic signal.

2. The semiconductor integrated circuit according to claim 1,

the load current detection circuit, the logic circuit, the gate voltage pull-down circuit, and the clamp withstand voltage reduction circuit operate using, as a power supply, an on control voltage applied to the gate of the semiconductor power switching element.

3. The semiconductor integrated circuit according to claim 1,

the load current detection circuit includes: a current sensing switching element that shunts a current proportional to the load current; a current detection resistor that outputs a detection signal obtained by converting the current shunted by the current sensing switching element into a voltage; and a hysteresis comparator which compares the detection signal with a reference voltage and outputs a low current detection signal when the detection signal is lower than the reference voltage.

4. The semiconductor integrated circuit according to claim 3,

the logic circuit outputs the logic signal when an input signal for controlling the conduction of the semiconductor power switching element is input and the low current detection signal generated in accordance with a decrease in the load current flowing due to the conduction of the semiconductor power switching element is input.

5. The semiconductor integrated circuit according to claim 1,

the gate voltage pull-down circuit includes a pull-down switching element connected between a gate of the semiconductor power switching element and a low potential terminal of the semiconductor power switching element, and turned on when receiving the logic signal.

6. The semiconductor integrated circuit according to claim 1,

the clamp withstand voltage reducing circuit includes a short-circuit switching element connected in parallel with a part of a plurality of diodes connected in series to constitute the clamp diode, and turned on when receiving the logic signal.

7. The semiconductor integrated circuit according to claim 1,

the semiconductor integrated circuit is an igniter in which the inductive load driven by the semiconductor power switching element is an ignition coil.

8. The semiconductor integrated circuit according to claim 1,

the semiconductor integrated circuit is a monolithic igniter in which the semiconductor power switching element, the load current detection circuit, the logic circuit, the gate voltage pull-down circuit, and the clamp withstand voltage reduction circuit are formed on the same semiconductor chip.

Technical Field

The present invention relates to a semiconductor integrated circuit including a voltage-controlled semiconductor power switching element for driving a coil load such as an ignition coil in an ignition system of an internal combustion engine for a vehicle.

Background

In an internal combustion engine for a vehicle using gasoline as a fuel, the following ignition system is used: a mixed gas of fuel and air filled in a combustion chamber of an internal combustion engine is ignited at a predetermined timing to be combusted.

Fig. 3 is a diagram showing an example of a configuration of a general ignition system.

The ignition system includes an igniter 100, an ignition coil 200 having a primary coil L1 and a secondary coil L2, and a spark plug 300. Terminals on the primary coil L1 and secondary coil L2 sides of the ignition coil 200 are connected to a positive terminal of the battery 500 via the switch 400, and a negative terminal of the battery 500 is connected to a chassis of the vehicle. The switch 400 includes an accessory switch, a relay switch provided in an electric device including the igniter 100, a fuse, and the like.

The other terminal of the primary coil L1 of the ignition coil 200 is connected to an output terminal OUT of the igniter 100, and an input terminal IN of the igniter 100 is connected to an Engine Control Unit (ECU) 600. In addition, the igniter 100 has a ground terminal GND and is connected to a negative terminal of the battery 500. The other terminal of the secondary coil L2 of the ignition coil 200 is connected to the center electrode of the spark plug 300, and the ground electrode of the spark plug 300 is screwed to the hood of the internal combustion engine and electrically grounded.

The igniter 100 includes a voltage-controlled semiconductor power switching element connected between the output terminal OUT and the ground terminal GND for switching operation. In the illustrated example, an IGBT (Insulated Gate Bipolar Transistor) 101 is used as the voltage control type semiconductor power switching element. As the voltage-controlled Semiconductor power switching element, another voltage-controlled Semiconductor power switching element such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) may be used. The IGBT101 has a collector connected to the output terminal OUT, a gate connected to the input terminal IN via the gate resistor 102, and an emitter connected to the ground terminal GND.

The igniter 100 further includes a control circuit 103 provided between the gate and emitter of the IGBT101 to perform a protection operation of the IGBT 101. The control circuit 103 operates with the input voltage Vin supplied to the gate of the IGBT101 as a power supply voltage, and only during a period when the input voltage Vin for controlling the IGBT101 to turn on is input. The igniter 100 further includes a clamping diode 104 for reverse voltage protection of the ignition coil 200 provided between the collector and gate of the IGBT101, and a diode 105 for electrostatic discharge protection provided between the input terminal IN and the emitter of the IGBT 101.

The engine control unit 600 includes an IGBT drive circuit 601 connected to the input terminal IN of the igniter 100 to drive the IGBT 101. The engine control unit 600 also has a plurality of ICs (Integrated circuits) 602, 603 required for controlling the internal combustion engine. These ICs 602 and 603 are processors used for signal processing for ignition timing control, fuel injection device control, intake/exhaust system control, valve train control, and start control of a starter motor, an antitheft system, and the like.

In the above ignition system, it is assumed that switch 400 is turned on and battery voltage VB of battery 500 is being supplied to engine control unit 600 and ignition coil 200. Here, when an input voltage Vin of, for example, 5 volts (V) is input from the IGBT drive circuit 601 to the input terminal IN of the igniter 100, the input voltage Vin is applied to the gate of the IGBT101 via the gate resistor 102. Thereby, the IGBT101 is turned on, and the primary coil L1 of the ignition coil 200 is energized. Thereafter, when the input voltage Vin becomes 0V at a predetermined timing, the IGBT101 is turned off, and the primary coil L1 of the ignition coil 200 is cut off. As a result, a high voltage is generated in the secondary coil L2 of the ignition coil 200, and this high voltage is supplied to the ignition plug 300, so that spark discharge is generated in the spark plug gap to ignite the air-fuel mixture in the combustion chamber. After that, by repeating the on and off of the IGBT101, spark discharge is intermittently generated.

The control circuit 103 operates with the input voltage Vin as a power supply voltage, and monitors the current flowing through the IGBT101 so that the current flowing through the IGBT101 does not exceed a predetermined current value. In order to detect the current flowing through the IGBT101, a device in which the IGBT101 is configured by combining a main IGBT and a sense IGBT is generally used (for example, see patent document 1). The sensing IGBT has the same configuration as the main IGBT, but the sensing IGBT has a smaller size than the main IGBT, and the gate and the collector of the sensing IGBT are connected together with the gate and the collector of the main IGBT. Thus, when a current flows to the main IGBT, a current substantially proportional to the current flowing through the main IGBT is shunted to the sense IGBT, and therefore the current flowing to the main IGBT can be indirectly detected by monitoring the current flowing through the sense IGBT. When detecting that the current flowing through the main IGBT exceeds a predetermined value, the control circuit 103 lowers the gate voltage applied to the IGBT101 to limit the current flowing through the main IGBT, thereby protecting the IGBT101 from being destroyed.

Disclosure of Invention

Technical problem

However, in the conventional ignition system, if the switch for supplying the battery voltage VB is accidentally turned off when the IGBT is turned on, there is a possibility that the circuit other than the igniter located on the downstream side of the switch may be broken. That is, when the IGBT is turned on and the switch is suddenly turned off, the ignition coil as an inductive load generates a back electromotive force, and the igniter-side terminal of the primary coil generates a positive high voltage with respect to the power supply line. At this time, although a current flows from the primary coil to the ground line via the IGBT of the igniter in the on state, a part of the current flows as a return current from the ground line to the IGBT drive circuit of the engine control unit via the diode for electrostatic discharge protection of the igniter. In addition, the remaining return current that is caused to flow to the ground line flows into the ground terminal of the IC of the engine control unit. That is, since a high voltage having a reverse polarity is applied to the power supply line and the ground line at the time when the switch is turned off, the engine control unit may be instantaneously destroyed.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a semiconductor integrated circuit in which, even when a switch is unexpectedly turned off when an igniter is turned on and a battery voltage is lost, other circuits under the control of the switch are not broken.

Technical scheme

In order to solve the above problems, the present invention provides a semiconductor integrated circuit. The semiconductor integrated circuit includes: a semiconductor power switching element that drives an inductive load; a load current detection circuit that detects a load current of an inductive load; a logic circuit that outputs a logic signal when the load current detection circuit detects a decrease in the load current when the semiconductor power switching element is turned on; a gate voltage pull-down circuit that pulls down a gate voltage of the semiconductor power switching element if the logic signal is received; and a clamp withstand voltage lowering circuit that switches, upon receiving the logic signal, a withstand voltage of a clamp diode provided between the gate of the semiconductor power switching element and a high-potential terminal of the semiconductor power switching element to which the inductive load is connected, to a low withstand voltage.

According to the semiconductor integrated circuit, when the load current detection circuit detects that the power supply line is cut off, the gate voltage pull-down circuit pulls down the gate voltage of the semiconductor power switching element, and the clamp withstand voltage lowering circuit sets the withstand voltage of the clamp diode low. Thus, the semiconductor power switching element is turned off at the timing when the power supply line is detected to be cut off, but the voltage of the high potential terminal generated by the turn-off is clamped to the low withstand voltage of the clamp diode, thereby protecting the semiconductor power switching element.

Technical effects

The semiconductor integrated circuit having the above configuration has the following advantages: even if the power supply line is cut off when the semiconductor power switching element is on, if the load current disappears, the voltage of the high potential terminal of the semiconductor power switching element disappears, and therefore, no backflow current is generated.

Drawings

Fig. 1 is a circuit diagram showing an example of the structure of an igniter according to an embodiment of the present invention.

Fig. 2 is a timing chart showing the operation of the igniter.

Fig. 3 is a diagram showing an example of a configuration of a general ignition system.

Description of the symbols

10 igniter

11 main IGBT

12 sense IGBT

13 collector current limiting circuit

14 reference voltage source

15 logic circuit

16-input identification circuit

17 control circuit

CMP hysteresis comparator

D1a, D1b clamp diode

GND grounding terminal

IN input terminal

M1, M2 semiconductor switch

OUT output terminal

Rg grid resistance

Rsns current detection resistor

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings, taking as an example a case where a semiconductor integrated circuit is applied to an igniter of an ignition system of an internal combustion engine for a vehicle. In the illustrated example, a case where an IGBT is used as a voltage control type semiconductor power switching element of an igniter is described, but a power MOSFET may be used.

Fig. 1 is a circuit diagram showing an example of the structure of an igniter according to an embodiment of the present invention. Fig. 2 is a timing chart showing the operation of the igniter.

The igniter 10 includes a main IGBT11 constituting a voltage-controlled semiconductor power switching element, and an IGBT12 indirectly detecting a collector current Ic as a load current flowing through the main IGBT 11. The collectors of the main IGBT11 and the sense IGBT12 are connected to the output terminal OUT, the gates of the main IGBT11 and the sense IGBT12 are connected to the terminal on one side of the gate resistance Rg, and the terminal on the other side of the gate resistance Rg is connected to the input terminal IN. Thus, when the input voltage Vin is input to the input terminal IN, the gate voltage Vgate is supplied to the gates of the main IGBT11 and the sense IGBT 12.

The emitter of the main IGBT11 is connected to the ground terminal GND, the emitter of the sense IGBT12 is connected to one terminal of the current detection resistor Rsns, and the other terminal of the current detection resistor Rsns is connected to the ground terminal GND. Thus, the current flowing through the sense IGBT12 is converted into a sense voltage Vsns by the current detection resistor Rsns, and becomes a detection signal. This detection signal is used to limit the collector current Ic and to detect the situation in which the battery-side switch is suddenly switched off and the battery voltage is lost.

The connection point between the emitter of the sense IGBT12 and the current detection resistor Rsns is connected to the input terminal of the collector current limiting circuit 13 and also connected to the non-inverting input terminal of the hysteresis comparator CMP, and is supplied with a sense voltage Vsns converted by the current detection resistor Rsns. The inverting input terminal of the hysteresis comparator CMP is connected to the positive terminal of the reference voltage source 14, and the negative terminal of the reference voltage source 14 is connected to the ground terminal GND. The reference voltage source 14 outputs a current flow detection level Vs1 and a current drop detection level Vs2(Vs1 > Vs2) as reference voltages of the hysteresis comparator CMP. The output terminal of the hysteresis comparator CMP is connected to the input terminal of the logic circuit 15 on one side, and the voltage Vcmp of the comparison result is supplied. When the detection signal based on the current detection resistor Rsns is lower than the reference voltage, the voltage Vcmp output from the hysteresis comparator CMP is supplied as a low current detection signal to the input terminal of the logic circuit 15.

The input terminal IN is connected to an input terminal of the input identification circuit 16, an output terminal of the input identification circuit 16 is connected to an input terminal on the other side of the logic circuit 15, and an input identification voltage Vin1 indicating that the input voltage Vin is being received is supplied. The output terminal of the logic circuit 15 is connected to the gates of the semiconductor switch M1 and the semiconductor switch M2, and supplies a logic output voltage Vlogic as a logic signal. The semiconductor switches M1 and M2 are N-channel MOSFETs. The drain of the semiconductor switch M1 is connected to the gates of the main IGBT11 and the sense IGBT12, and the source of the semiconductor switch M1 is connected to the ground terminal GND. When turned on, the semiconductor switch M1 lowers the gate voltage Vgate to the ground potential, thereby constituting a gate voltage pull-down circuit.

The collectors of the main IGBT11 and the sense IGBT12 are connected to the cathode of the clamp diode D1a, and the anode of the clamp diode D1a is connected to the cathode of the clamp diode D1 b. The anode of the clamp diode D1b is connected to the gates of the main IGBT11 and the sense IGBT 12.

The connection point of the anode of the clamp diode D1a and the cathode of the clamp diode D1b is connected to the drain of the semiconductor switch M2, and the source of the semiconductor switch M2 is connected to the anode of the clamp diode D1 b. Thus, when the semiconductor switch M2 is turned off, the collector-gate voltage of the main IGBT11 and the sense IGBT12 is clamped by the total breakdown voltage (withstand voltage) of the clamp diode D1a and the clamp diode D1 b. Since both terminals of the clamp diode D1b are short-circuited when the semiconductor switch M2 is turned on, the collector-gate voltage of the main IGBT11 and the sense IGBT12 is clamped to the withstand voltage of the clamp diode D1 a. Note that, in order to make each of the clamp diode D1a and the clamp diode D1b have a high withstand voltage, a plurality of zener diodes are connected in series. For example, the total withstand voltage of the clamp diode D1a and the clamp diode D1b is about 400V to 500V. The withstand voltages of the clamp diode D1a and the clamp diode D1b are considered factors for the system represented by fig. 3, and are set as appropriate. The voltage resistance of the clamping diode D1b is preferably equal to or less than the voltage resistance of the semiconductor switch M2. The clamp diode D1b preferably has a withstand voltage of 50V or less.

Collector current limiting circuit 13 receives sense voltage Vsns as an input, and when sense voltage Vsns exceeds a predetermined threshold value, that is, when collector current Ic exceeds a predetermined value, controls gate voltage Vgate to be decreased so as to limit collector current Ic so that collector current Ic equal to or larger than the predetermined value does not flow.

In the igniter 10, the current detection resistor Rsns, the collector current limiting circuit 13, the hysteresis comparator CMP, the reference voltage source 14, the logic circuit 15, the semiconductor switch M1, and the semiconductor switch M2 constitute a control circuit 17 corresponding to the control circuit 103 of the igniter 100 shown in fig. 3. The igniter 10 is a monolithic igniter in which the main IGBT11, the sense IGBT12, the gate resistor Rg, the clamp diode D1a, the clamp diode D1b, the input discrimination circuit 16, and the control circuit 17 are formed on the same semiconductor chip.

Here, the sense IGBT12, the current detection resistor Rsns, the hysteresis comparator CMP, and the reference voltage source 14 of the igniter 10 constitute a load current detection circuit. In this load current detection circuit, when a decrease in the current of the sense IGBT12 is detected, that is, when a decrease in the sense voltage Vsns generated by the current detection resistor Rsns is detected, the battery voltage of the power supply line disappears, and the sense IGBT12 shunts the load current that flows when the main IGBT11 is turned on.

When the logic circuit 15 receives the input identification voltage Vin1 and the low current detection signal and outputs a logic signal of the logic output voltage Vlogic, the semiconductor switch M1 is turned on. Thereby, the gate voltage Vgate of the main IGBT11 is pulled down, and the main IGBT11 is rapidly turned off.

Upon receiving the logic signal of the logic output voltage Vlogic, the semiconductor switch M2 is turned on, and both terminals of the clamp diode D1b are short-circuited to lower the clamp withstand voltage. Thus, the collector voltage Vc that rises as the main IGBT11 is rapidly turned off is clamped by the clamp diode D1a, and the collector voltage Vc is not set to a high voltage as compared with the withstand voltage of the clamp diode D1 a. At this time, since the gate capacitance of the main IGBT11 is charged by the current flowing through the clamp diode D1a, the main IGBT11 gradually cuts off the collector current Ic with a delay in the decrease of the gate voltage Vgate of the main IGBT 11.

Next, with reference to fig. 2, an operation when the igniter 10 is applied to the ignition system shown in fig. 3 will be described. In fig. 2, starting from the top, the switching of the power supply line, the input identification voltage Vin1, the sense voltage Vsns, the voltage Vcmp output by the hysteresis comparator CMP, the logic output voltage Vlogic, the gate voltage Vgate, the collector current Ic of the main IGBT11, and the collector voltage Vc are shown.

First, the igniter 10 is used with the switch in an on state. Here, when the input voltage Vin is at a low (L) level to turn off the main IGBT11, the input identification voltage Vin1 and the gate voltage Vgate are also at an L level. At this time, since collector current Ic is 0, sensing voltage Vsns and voltage Vcmp of hysteresis comparator CMP are also at L level. The collector voltage Vc of the main IGBT11 becomes equal to the battery voltage VB.

At time t0, when the input voltage Vin is input from the IGBT drive circuit of the engine control unit to the input terminal IN of the igniter 10, the input identification voltage Vin1 and the gate voltage Vgate become the high (H) level. Accordingly, the main IGBT11 and the sense IGBT12 are turned on, and the collector voltage Vc rapidly decreases, whereas the load of the igniter 10 is an inductive ignition coil, and the collector current Ic gradually increases.

Thereafter, collector current Ic gradually rises, and when sensing voltage Vsns exceeds current conduction detection level Vs1, hysteresis comparator CMP outputs voltage Vcmp at the H level.

At time t1, when the power supply line is switched off for some reason, collector current Ic gradually decreases, and accordingly, sense voltage Vsns also gradually decreases.

At time t2, if the sense voltage Vsns is lower than the current reduction detection level Vs2, the hysteresis comparator CMP outputs the voltage Vcmp of the L level. Thus, the logic circuit 15 outputs the logic output voltage Vlogic at the H level at this point in time as a case where the current decreases due to the power supply line being cut.

When the logic circuit 15 outputs the logic output voltage Vlogic at the H level, the semiconductor switch M1 is turned on, and the gate voltage Vgate is pulled down instantaneously. Thereby, main IGBT11 turns off and collector current Ic momentarily decreases, and collector voltage Vc momentarily rises. At the same time, the semiconductor switch M2 is also turned on to switch the withstand voltages of the clamp diode D1a and the clamp diode D1b to the withstand voltage of only the clamp diode D1a, so that the collector voltage Vc is clamped to the withstand voltage of the clamp diode D1a, and the current of the clamp diode D1a is abruptly increased. By supplying the current of the clamp diode D1a to the gate of the main IGBT11, the collector current Ic is gradually decreased while suppressing the decrease in the gate voltage Vgate, and the sense voltage Vsns is also gradually decreased. Thereafter, when collector current Ic becomes 0 at all, collector voltage Vc also falls to 0.

When the input voltage Vin of L level is input to the input terminal IN at time t3, the input identification voltage Vin1 and the gate voltage Vgate become L level, and the logic circuit 15 outputs the logic output voltage Vlogic of L level.

For reference, fig. 2 shows the operation of gate voltage Vgate, sense voltage Vsns, collector current Ic, and collector voltage Vc generated by the conventional igniter by a curve indicated by a one-dot chain line. That is, when the power supply line is cut off, sense voltage Vsns, collector current Ic, and collector voltage Vc gradually decrease, and when collector current Ic decreases to 0, the polarity of collector voltage Vc is inverted, and a negative voltage is generated. At this time, since the main IGBT11 is in the on state when the gate voltage Vgate is kept at the H level, the power supply line of the ignition coil and the main IGBT11 becomes a negative electrode, and the ground line of the emitter of the main IGBT11 becomes a positive electrode. Thus, since a voltage of opposite polarity is applied to the power supply line and the ground line, the engine control unit connected to the power supply line and the ground line may be broken.