Power switching control device for electric systems
A power switching control device for electric systems such as an ignition device for internal combustion engines has a control circuit IC and a switching IC. A temperature sensor is provided in the switching IC. The control circuit IC is joined to a grounding terminal through a conductive layer provided therebetween. Thus, the substrate potential of the control circuit IC is stabilized to the ground potential so that the temperature sensor is prohibited to operate erroneously due to electromagnetic noise.
1. A power switching control device comprising:
a switching IC including a semiconductor power switching element, which turns on and off supply of coil current to an ignition coil, the switching IC including a temperature sensor constructed with at least one diode for detecting temperature of the switching IC;
a control circuit IC provided in a chip form separate from the switching IC for outputting a control signal to turn on and off the switching element, the control circuit IC generating the control signal in response to an ignition signal applied thereto, the control circuit IC including an overheat detector circuit for detecting an overheating of the switching IC based on a detection result of the temperature sensor and controlling the control signal to stop an operation of the switching element upon detection of the overheating;
a bonding wire connecting the temperature sensor and the overheat detector circuit;
a grounding terminal grounding the switching element and the temperature sensor, the grounding terminal further grounding the overheat detector circuit through the bonding wire and the switching IC; and
a conductive layer provided between the control circuit IC and the grounding terminal to join the control circuit IC to the grounding terminal.
2. The power switching control device according to claim 1 , wherein the conductive layer is a solder.
3. The power switching control device according to claim 1 , wherein the conductive layer is a conductive adhesive.
4. The power switching control device according to claim 1 , wherein the diode is a polysilicon diode and formed on the switching IC.
5. The power switching control device according to claim 1 , wherein the overheat detector circuit compares a terminal voltage of the temperature sensor with a predetermined voltage and detects the overheating when the terminal voltage becomes smaller than the predetermined voltage.
6. The power switching control device according to claim 1 , wherein the grounding terminal is formed as a terminal of a lead frame.
7. The power switching control device according to claim 1 , wherein the bonding wire is shorter than 5 mm in length.
8. A power switching control device comprising:
a switching IC including a semiconductor power switching element, which turns on and off supply of coil current to an ignition coil, the switching IC including a temperature sensor constructed with at least one diode for detecting temperature of the switching IC;
a control circuit IC provided in a chip form separate from the switching IC for outputting a control signal to turn on and off the switching element, the control circuit IC generating the control signal in response to an ignition signal applied thereto, the control circuit IC including an overheat detector circuit for detecting an overheating of the switching IC based on a detection result of the temperature sensor and controlling the control signal to stop an operation of the switching element upon detection of the overheating;
a bonding wire connecting the temperature sensor and the overheat detector circuit; and
a grounding terminal grounding the switching element and the temperature sensor, the grounding terminal further grounding the overheat detector circuit through the bonding wire and the switching IC,
wherein the bonding wire is shorter than 5 mm in length.
9. A power switching control device comprising:
a switching IC including a semiconductor power switching element, which turns on and off supply of current to an electric system, the switching IC including a temperature sensor for detecting temperature of the switching element;
a control circuit IC distanced from the switching IC for controlling operation of the switching element, the control circuit IC including an overheat detector circuit for detecting an overheating of the switching IC based on a detection result of the temperature sensor and stopping the operation of the switching element upon detection of the overheating;
bonding wires connecting the switching IC and the control circuit IC to each other;
a grounding terminal for grounding both the switching IC and the control circuit IC; and
a conductive layer provided between the control circuit IC and the grounding terminal and joining the control circuit IC to the grounding terminal thereby grounding the control circuit IC.
10. The power switching control device according to claim 9 , wherein the conductive layer has resistance of less than 1 kΩ and capacitance of more than 10 pF.
11. The power switching control device according to claim 9 , wherein the bonding wires are shorter than 5 mm in length.
12. The power switching control device according to claim 9 , wherein the switching element is a vertical-type IGBT, and the temperature sensor includes a plurality of diodes provided to be responsive to temperature of the IGBT.