Semiconductor integrated circuit having a plurality of transistors
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：提供半导体集成电路。能针对对电源短路故障、像浪涌电压那样在短时间急剧变化的高电压保护功率开关元件和控制电路。点火器(1)在输入端子(IN)与控制电路(12)的电源端子之间具有第1降压电路(15),在输入端子(IN)与IGBT(11)的栅极之间具有第2降压电路(16)。若因对电源短路故障而向输入端子(IN)输入电池电压,则第1降压电路(15)将电池电压降压到控制电路(12)的电源电压。如果因对电源短路故障而向输入端子输入电池电压,则第2降压电路(16)将电池电压降压到IGBT(11)的栅极电压。针对浪涌电压,以齐纳二极管组(13)以及第1降压电路(15)和第2降压电路(16)这两级结构进行减压。(A semiconductor integrated circuit is provided. The power switching element and the control circuit can be protected against a high voltage which abruptly changes in a short time like a surge voltage against a power supply short-circuit fault. The igniter (1) has a 1 st step-down circuit (15) between an input terminal (IN) and a power supply terminal of the control circuit (12), and has a 2 nd step-down circuit (16) between the input terminal (IN) and a gate of the IGBT (11). When a battery voltage is input to an input terminal (IN) due to a short-circuit failure to a power supply, a 1 st step-down circuit (15) steps down the battery voltage to a power supply voltage of a control circuit (12). If a battery voltage is input to the input terminal due to a short-circuit fault to the power supply, a 2 nd step-down circuit (16) steps down the battery voltage to the gate voltage of the IGBT (11). The voltage of the surge voltage is reduced by a two-stage structure of a Zener diode group (13), a 1 st voltage reduction circuit (15) and a 2 nd voltage reduction circuit (16).)
1. A semiconductor integrated circuit is provided with:
a power switching element;
a control circuit that uses a gate voltage for controlling the power switching element as a power supply voltage;
an electrostatic discharge protection device connected to an input terminal to which the gate voltage is input and protecting the power switching element and the control circuit from being damaged by electrostatic discharge; and
a power supply short-circuit protection circuit that protects the power switching element and the control circuit from being damaged by a high voltage caused by a power supply short-circuit fault when the high voltage is input,
the pair of power supply short-circuit protection circuits has:
a 1 st step-down circuit that is arranged between an input terminal to which the gate voltage is input and the control circuit, and that steps down the high voltage to a voltage close to a voltage of the power supply voltage of the control circuit when the high voltage is input; and
and a 2 nd step-down circuit which is arranged between the input terminal and the gate of the power switching element, and which steps down the high voltage to a voltage close to the gate voltage when the high voltage is input.
2. The semiconductor integrated circuit according to claim 1, wherein the 1 st step-down circuit and the 2 nd step-down circuit have a plurality of stages of step-down sections that sequentially step down the high voltage input to the input terminal.
3. The semiconductor integrated circuit according to claim 2, wherein the voltage step-down section arranged on the input terminal side has a 1 st resistor, a 2 nd resistor, and a 1 st zener diode connected in series.
4. The semiconductor integrated circuit according to claim 3, wherein the voltage step-down section provided in the final stage has a 3 rd resistor and a 2 nd zener diode connected in series, and clamps the voltage received from the previous stage to a breakdown voltage of the 2 nd zener diode.
5. The semiconductor integrated circuit according to claim 1, wherein the semiconductor integrated circuit has a pull-down resistor connected in parallel with the electrostatic discharge protection device.
6. The semiconductor integrated circuit according to claim 1, wherein the semiconductor integrated circuit is an igniter that controls the power switching element to energize or deenergize an ignition coil.
Technical Field
The present invention relates to a semiconductor integrated circuit as an igniter including a power switching element for driving a load such as an ignition coil of an ignition system of an internal combustion engine for a vehicle and a control circuit for protecting the power switching element.
Background
The igniter includes a semiconductor power switching element that is capable of generating a high voltage for electrically discharging the spark plug in a secondary coil by energizing or interrupting a primary coil of an ignition coil. As the power switching element, a voltage control type semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor) is used. As the power switching element, another voltage-controlled Semiconductor element such as a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) may be used.
In the igniter, the power switching element is turned on by applying a gate voltage to the input terminal, and is turned off when the gate voltage is not applied. In this case, the control circuit for protecting the power switching element includes a control circuit that operates using the gate voltage applied to the input terminal as a power supply, and in this type of igniter, when the gate voltage is not applied, the operation of the control circuit is stopped.
The igniter is also provided in the vicinity of the internal combustion engine, is connected to an Engine Control Unit (ECU) via a harness, and is controlled by a gate voltage supplied from the engine control Unit. Therefore, only the gate voltage is supplied from the engine control unit to the igniter. However, in the wire harness on the engine control unit side, a wire for supplying power to another circuit device may come into contact with a signal line for a gate voltage connected to an input terminal of the igniter. In this case, a short-circuit failure to the power supply may occur, such as a direct application of the battery voltage to the input terminal of the igniter.
In the igniter, the power switching element and the control circuit operate at a low gate voltage of, for example, about 5 volts (V), but if a short-circuit failure occurs to the power supply, a high voltage, which is a battery voltage, is applied, and therefore, depending on the case, destruction may occur.
Therefore, an igniter is known which protects the power switching element and the control circuit from damage even if there is a short-circuit failure to the power supply (see, for example, patent document 1). According to patent document 1, a short-circuit protection circuit for a power supply is provided between an input terminal to which a gate voltage is input and a gate of a power switching element, and between the input terminal and a control circuit that operates the gate voltage of the power switching element as a power supply voltage. The pair of power supply short-circuit protection circuits includes a 1 st voltage division circuit for dividing a voltage applied to an input terminal to a low voltage, a switching element connected in series with the 1 st voltage division circuit for activating or deactivating the 1 st voltage division circuit, and a 2 nd voltage division circuit for detecting the voltage applied to the input terminal. Here, when the voltage applied to the input terminal is a normal gate voltage, the 2 nd voltage dividing circuit turns off the switching element, and the 1 st voltage dividing circuit functions only as a part of the gate resistance connected to the gate of the power switching element. On the other hand, if the 2 nd voltage dividing circuit detects that the voltage applied to the input terminal becomes a predetermined voltage or more, the switching element is turned on and the 1 st voltage dividing circuit becomes active. Thus, the input voltage is divided to a value close to the gate voltage, and thus the power switching element and the control circuit of the igniter are protected from being broken by the application of the high voltage even if there is a short-circuit failure to the power supply.
In the igniter of patent document 1, a circuit for protecting against a surge voltage typified by electrostatic Discharge (ESD) is provided at an input terminal to which a gate voltage is input. The protection circuit is composed of a zener diode, and is turned on to absorb a surge voltage if the surge voltage exceeding the breakdown voltage of the zener diode is applied to the input terminal.
As described above, the igniter of patent document 1 includes a power supply short-circuit protection circuit and a zener diode for surge voltage protection at an input terminal. Thus, the power switching element and the control circuit are protected from a relatively high dc voltage by the power supply short-circuit protection circuit, and are protected from a pulse-like surge voltage by the zener diode.
Disclosure of Invention
Technical problem
Existing igniters utilize zener diodes to protect against surge voltages to some extent. However, if the operating resistance of the zener diode at this time is taken into consideration, a voltage drop due to the operating resistance of the zener diode is added to the breakdown voltage of the zener diode in the power supply short-circuit protection circuit. Since this voltage is a voltage which is higher than a voltage at the time of occurrence of a power supply short-circuit fault and which abruptly changes so as not to follow a protection operation of the power supply short-circuit protection circuit, such a voltage is input to the power supply short-circuit protection circuit. In the power supply short-circuit protection circuit, the 2 nd voltage dividing circuit detects a rapidly changing high voltage to turn on the switching element, and thereafter, the 1 st voltage dividing circuit is activated, so that there is a problem that an operation delay due to the active element inevitably occurs, and the high voltage is propagated to the inside during the operation delay.
The present invention has been made in view of such circumstances, and an object thereof is to provide a semiconductor integrated circuit including a power supply short-circuit protection circuit capable of protecting a power switching element and a control circuit against a high voltage which abruptly changes in a short time such as a surge voltage.
Technical scheme
In order to solve the above problems, the present invention provides, in 1 aspect, a semiconductor integrated circuit including: a power switching element; a control circuit for controlling a gate voltage of the power switching element as a power supply voltage; an electrostatic discharge protection device connected to an input terminal to which a gate voltage is input and protecting the power switching element and the control circuit from being damaged by electrostatic discharge; and a power supply short-circuit protection circuit that protects the power switching element and the control circuit from being damaged by a high voltage when the high voltage caused by a power supply short-circuit fault is input. The circuit for protecting a power supply short circuit of a semiconductor integrated circuit includes: a 1 st step-down circuit which is arranged between an input terminal to which a gate voltage is input and the control circuit, and which, when a high voltage is input, steps down the high voltage to a voltage close to a voltage of a power supply voltage of the control circuit; and a 2 nd step-down circuit which is disposed between the input terminal and the gate of the power switching element, and which steps down the high voltage to a voltage close to the gate voltage when the high voltage is input.
Effects of the invention
In the semiconductor integrated circuit having the above configuration, the 1 st step-down circuit and the 2 nd step-down circuit step down not only a high voltage due to a short-circuit fault to a power supply but also a high voltage abruptly changed and clamped by the electrostatic discharge protection device, and therefore, there is an advantage that an applied surge voltage does not propagate to the inside. Further, since the 1 st step-down circuit protects the power supply voltage to the control circuit and the 2 nd step-down circuit protects the gate voltage to the power switching element, it is easy to design step-down circuits suitable for the power switching element and the control circuit, respectively.
Drawings
Fig. 1 is a diagram showing an example of the configuration of an ignition system including an igniter according to an embodiment of the present invention.
Fig. 2 is a diagram showing an example of the 1 st step-down circuit.
Fig. 3 is an explanatory diagram for explaining a step-down state at the time of high voltage input of the 1 st step-down circuit.
Description of the symbols
1: igniter
2: ignition coil
3: spark plug
4: battery with a battery cell
11：IGBT
12: control circuit
13: zener diode group
14: pull-down resistor
15: no. 1 step-down circuit
16: no. 2 step-down circuit
17: grid resistance
18: accelerating diode
19: switching element
D11, D12: zener diode
GND: grounding terminal
IN: input terminal
OUT: output terminal
R1a, R1b, R1 c: resistance (RC)
Detailed Description
Hereinafter, embodiments of the present invention will be described in detail by 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, with reference to the drawings. In the illustrated example, the case where an IGBT is used for the power switching element of the igniter is described, but a power MOSFET may be used.
Fig. 1 is a diagram showing a configuration example of an ignition system including an igniter according to an embodiment of the present invention, fig. 2 is a diagram showing an example of a 1 st step-down circuit, and fig. 3 is an explanatory diagram explaining a step-down state at the time of high voltage input of the 1 st step-down circuit.
The ignition system includes an igniter 1, an ignition coil 2, and an ignition plug 3, and a positive terminal of a battery 4 is connected to one terminal of a primary coil and a secondary coil of the ignition coil 2. The battery 4 is a battery for an automobile that outputs a voltage of, for example, 12V. The igniter 1 is controlled to energize or deenergize the ignition coil 2 based on the gate voltage supplied from the engine control unit. The ignition coil 2 causes a current supplied from the battery 4 to flow through the primary coil when energized, thereby turning the primary coil into an electromagnet, and generates a flux bundle inside a magnetic core around which the primary coil is wound. When the igniter 1 cuts off the ignition coil 2 at a predetermined ignition timing, the magnetic flux in the magnetic core suddenly disappears, and thereby a high voltage due to electromagnetic induction is generated in the secondary coil wound around the same magnetic core. If this high voltage is applied to the ignition plug 3, the ignition plug 3 generates an electric discharge in its gap, igniting and burning the mixture gas in the combustion chamber of the engine.
The igniter 1 includes an IGBT 11 as a power switching element and a control circuit 12 for protecting the IGBT, but in this embodiment, the gate voltage controlling the IGBT 11 is configured to operate as a power supply for the control circuit 12. Therefore, the igniter 1 has an input terminal IN to which a gate voltage is applied, an output terminal OUT connected to the primary coil of the ignition coil 2, and a ground terminal GND connected to the chassis of the vehicle, and does not have a power supply terminal for the control circuit 12.
The input terminal IN of the igniter 1 is connected to the cathode of a
The input terminal IN is also connected to one terminal of the pull-down resistor 14, and the other terminal of the pull-down resistor 14 is connected to the ground terminal GND. The pull-down resistor 14 is useful when the engine control unit includes a single transistor constituting an output circuit of the drive circuit. In other words, when the output circuit of the driver circuit is formed by 1 transistor, the impedance of the output circuit is increased only by not supplying a voltage to the gate when the IGBT 11 is turned off. At this time, the pull-down resistor 14 can discharge the electric charge accumulated in the gate capacitance of the IGBT 11, and therefore, the gate voltage can be quickly lowered to the threshold voltage of the IGBT 11 or less. In the case where the output circuit of the drive circuit in the engine control unit has a push-pull circuit configuration, the contribution of the action of the pull-down resistor 14 is small. This is because, when the IGBT 11 is turned off, the low-potential transistor of the push-pull draws the charge accumulated in the gate capacitance of the IGBT 11 as a sink current, and thus, there is no need to discharge the charge by the pull-down resistor 14.
The input terminal IN is also connected to an input of the 1 st step-down circuit 15 and an input of the 2 nd step-down circuit 16 constituting a protection circuit for power supply short-circuiting. The output of the 1 st step-down circuit 15 is connected to the power supply terminal of the control circuit 12, and the output of the 2 nd step-down circuit 16 is connected to one terminal of the gate resistor 17 and the cathode of the acceleration diode 18. The low-potential-side terminals of the 1 st step-down circuit 15 and the 2 nd step-down circuit 16 are connected to the ground terminal GND, respectively. These 1 st step-down circuit 15 and 2 nd step-down circuit 16 operate only when the battery voltage or the surge voltage is applied to the input terminal IN, and do not operate at all when the normal gate voltage is applied.
The other terminal of the gate resistor 17 and the anode of the accelerator diode 18 are connected to the gate of the IGBT 11, the collector of the IGBT 11 is connected to the output terminal OUT, and the emitter of the IGBT 11 is connected to the ground terminal GND. When the IGBT 11 is turned off, the accelerator diode 18 short-circuits the gate resistor 17 by a current flowing from the gate of the IGBT 11 to the input terminal IN, thereby speeding up the operation of the IGBT 11 when turned off.
An output terminal of the control circuit 12 is connected to a gate of the switching element 19. The switching element 19 may be, for example, an N-channel MOSFET, the drain of which is connected to the gate of the IGBT 11, and the source of the switching element 19 is connected to the emitter of the IGBT 11. The control circuit 12 and the switching element 19 are used to forcibly reduce the gate voltage of the IGBT 11 based on an abnormality detection signal from a circuit, not shown, that detects an overcurrent state or an overheat of the IGBT 11 or a high-lock state of an input signal generated by a timer, thereby protecting the IGBT 11 from being broken.
According to the igniter 1 configured as described above, if a gate voltage of, for example, 5V is applied from the engine control unit, the gate voltage is applied to the gate of the IGBT 11 via the 2 nd step-down circuit 16 and the gate resistor 17. Thus, if the gate capacitance of the IGBT 11 is charged and the IGBT 11 is turned on, the current supplied from the battery 4 flows to the ground through the primary coil of the ignition coil 2 and the IGBT 11, and a magnetic flux is generated inside the core of the ignition coil 2.
Thereafter, if a gate voltage of 0V is applied from the engine control unit, the charge accumulated in the gate capacitance of the IGBT 11 is consumed by the pull-down resistor 14 via the accelerator diode 18 and the 2 nd step-down circuit 16. Alternatively, the charge accumulated in the gate capacitor is pumped to the engine control unit via the accelerating diode 18 and the 2 nd step-down circuit 16. Accordingly, since the IGBT 11 is turned off, the magnetic flux in the core of the ignition coil 2 is abruptly lost, and thus a high voltage is generated in the secondary coil of the ignition coil 2 by electromagnetic induction, and discharge occurs in the gap of the ignition plug 3.
As described above, the IGBT 11 repeats on and off, and the spark plug 3 can be discharged periodically and continuously. When the IGBT 11 is repeatedly turned on and off, if the control circuit 12 detects any abnormality, the control circuit 12 turns on the switching element 19, thereby forcibly lowering the gate voltage of the IGBT 11 to turn off the IGBT 11. This protects the igniter 1 from the element destruction of the IGBT 11 due to the occurrence of an abnormality.
Next, a specific example of the 1 st step-down circuit 15 and the 2 nd step-down circuit 16 as the power supply short-circuit protection circuit will be described. Since the 1 st step-down circuit 15 and the 2 nd step-down circuit 16 have the same circuit configuration, the 1 st step-down circuit 15 will be representatively described herein.
The 1 st step-down circuit 15 includes resistors R1a, R1b, R1c, and zener diodes D11, D12 in the configuration example shown in fig. 2. One terminal of the resistor R1a is connected to the input terminal IN, the other terminal of the resistor R1a is connected to one terminal of the resistor R1b, the other terminal of the resistor R1b is connected to the cathode of the zener diode D11, and the anode of the zener diode D11 is connected to the ground terminal GND. The other terminal of the resistor R1a is also connected to one terminal of the resistor R1c, the other terminal of the resistor R1c is connected to the cathode of the zener diode D12, and the anode of the zener diode D12 is connected to the ground terminal GND. Here, the resistors R1a and R1c, which are always connected to the control circuit 12, are set to values that can obtain a required voltage drop in consideration of the current consumption of the control circuit 12, and the resistors R1a and R1b determine the voltage division ratio when the voltage is reduced with respect to the battery voltage.
First, IN the 1 st step-down circuit 15, when the gate voltage lower than the breakdown voltage of the zener diodes D11 and D12 is input to the input terminal IN, the zener diodes D11 and D12 do not conduct. Therefore, the gate voltage is supplied to the control circuit 12 via the series circuit of the resistors R1a and R1 c. On the other hand, when the battery voltage is input to the input terminal IN, the 1 st step-down circuit 15 steps down the input voltage V0 to the voltage V11 by the step-down section of the 1 st stage, and steps down the voltage V11 to the voltage V12 by the step-down section of the 2 nd stage to supply power to the control circuit 12. The voltage V12 at this time is equal to the breakdown voltage of the zener diode D12, and is a voltage close to the power supply voltage of the control circuit 12.
Here, the zener diodes D11 and D12 have breakdown voltages of about 6V, respectively, as in the case of the zener diodes constituting the
The 1 st step-down circuit 15 is not provided with an element that causes a delay from the time when a surge voltage is applied to the circuit to the time when a protection operation is started, such as a transistor, but is configured with only an element having a good response that can substantially ignore the delay operation. Therefore, the 1 st step-down circuit 15 can protect not only the short-circuit protection of the battery voltage against the power supply but also a high voltage that abruptly changes in a short time such as a surge voltage.
Next, with reference to fig. 2 and 3, a description will be given of how the 1 st step-down circuit 15 absorbs energy and lowers the voltage supplied to the control circuit 12 when the battery voltage is input to the input terminal IN of the igniter 1. IN fig. 2, a voltage V0 is a voltage input to the input terminal IN, a voltage V11 is a voltage stepped down by the step-down section of the 1 st stage of the 1 st step-down circuit 15, and a voltage V12 is a voltage stepped down by the step-down section of the 2 nd stage. The current I0 is a current flowing through the
When the battery voltage is input to the input terminal IN of the igniter 1, the battery voltage is first applied to the
Next, in the 1 st step-down circuit 15, the load line of the resistor R1a of the step-down unit of the 1 st stage is represented by a straight line starting from the voltage V0, and the relationship between the voltage drop and the current with respect to the total of the operating resistance of the zener diode D11 and the resistor R1b is represented by a straight line starting from the voltage Vz. Therefore, the voltage dropped by the voltage drop unit of the 1 st stage becomes the voltage V11 at the intersection of these straight lines from the voltage V0, and at this time, the current flowing through the resistor R1b and the zener diode D11 becomes the current I11.
Next, in the step-down section of the 2 nd stage, the load line of the resistor R1c is represented by a straight line starting from the voltage V11, and the relationship between the voltage drop with respect to the operating resistance of the zener diode D12 and the current is represented by a straight line starting from the voltage Vz. Therefore, the voltage dropped by the step-down unit of the 2 nd stage becomes the voltage V12 at the intersection of these straight lines from the voltage V11, and at this time, the current flowing through the zener diode D12 becomes the current I12. That is, when the battery voltage is input, the voltage V12 output from the 1 st step-down circuit 15 is a voltage obtained by adding a voltage drop due to the operating resistance of the zener diode D12 to the breakdown voltage of the zener diode D12. The breakdown voltage of the zener diode D12 is about 6V, and since the voltage drop due to the operating resistance of the zener diode D12 is considerably small, the battery voltage input to the input terminal IN is clamped to a voltage of about 6V, thereby performing short-circuit protection of the power supply.
When the surge voltage is input to the input terminal IN, the voltage V0 higher than the voltage of 3 × Vz is input to the 1 st step-down circuit 15 due to the operating resistance of the
The 2 nd step-down circuit 16 also has the same circuit configuration as the 1 st step-down circuit 15, but is optimized for its resistance value so that the applied surge voltage is reduced to a voltage close to the voltage to be applied to the gate of the IGBT 11. Since the 2 nd step-down circuit 16 has the same circuit configuration as the 1 st step-down circuit 15, the operation when the battery voltage or the surge voltage is input to the input terminal IN is the same as the operation of the 1 st step-down circuit 15 described above.
The reason why the igniter 1 has the 1 st step-down circuit 15 and the 2 nd step-down circuit 16 having the same function as the power supply short-circuit protection circuit is that the gate voltage inputted to the input terminal IN is used differently. That is, while the control circuit 12 performs a protection operation using the gate voltage as a power supply while the gate voltage is input, the IGBT 11 either supplies a source current to the gate or draws a sink current from the gate. Therefore, in the igniter 1, in order to prevent a voltage drop caused by the consumed current of the control circuit 12 from directly affecting the reduction of the gate voltage of the IGBT 11, in particular, the 1 st step-down circuit 15 for the control circuit 12 and the 2 nd step-down circuit 16 for the IGBT 11 are provided.
In the configuration example shown in fig. 2, the 1 st step-down circuit 15 is configured by 2 stages, i.e., a step-down unit configured by the resistors R1a, R1b and the zener diode D11 and a step-down unit configured by the resistor R1c and the zener diode D12. However, the number of stages of the 1 st step-down circuit 15 is not limited to these 2 stages, and may be configured by, for example, 3 or more step-down units depending on the battery voltage.
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