Patent ID: 8994220
Filing Date: 2015-03-31
Classification: B60R

Abstract:
1. A vehicle-mounted electronic control device comprising: a switching element constituting a switching power supply which is operated using a power supply voltage fed from a vehicle-mounted battery as an input voltage and is for stepping down the power supply voltage to generate a predetermined intermediate voltage; a continuously controlled type first constant voltage controlled power supply or a same type second constant voltage controlled power supply, which is connected in series to a later stage of said switching element and generates a first stabilization voltage or a second stabilization voltage; and a control circuit unit including a main control circuit section which is fed from said second constant voltage controlled power supply and has at least a microprocessor, a program memory, and a RAM memory, or a subsidiary control circuit section which is fed from said first constant voltage controlled power supply and is operative in cooperation with said main control circuit section, wherein a downstream side coil serving as an inductive element is connected in series between said switching element and said first constant voltage controlled power supply or between said switching element and said second constant voltage controlled power supply; a flywheel diode is connected between said downstream side coil and a ground circuit on the upstream side of said downstream side coil; an output capacitor is connected between said downstream side coil and said ground circuit on the downstream side of said downstream side coil; a value of an induced time constant which is a ratio between inductance of said downstream side coil and load resistance of an electric load fed from said switching element uses a value larger than a switching cycle at which switching control of said switching element is performed; said switching element is a P channel type or an N channel type field effect transistor; a circuit for suppressing reverse conduction is connected to a gate circuit of said field effect transistor; a reset circuit which is for initializing at least said microprocessor when the intermediate voltage is lowered to less than a predetermined value is provided; when the power supply voltage is temporarily and abnormally lowered, charging electric charge of said output capacitor is flown back to the upstream power supply side by reverse conduction of said switching element to suppress from generating an undershoot; and said reset circuit prevents said microprocessor from being initialized by the undershoot of said output capacitor.