Apparatus for controlled switching of a microcomputer to standby mode

• US 5,375,247 A
• Filed: 01/03/1991
• Issued: 12/20/1994
• Est. Priority Date: 07/28/1988
• Status: Expired due to Fees

• Current Assignee: Robert Bosch GmbH
• Original Assignee: Robert Bosch GmbH
• Inventors: Hueser, Klaus
• Primary Examiner(s): MacDonald, Allen R.
• Assistant Examiner(s): DAVIS, GEORGE B
• Application Number:
  US07/635,183
• Time in Patent Office: 1,447 Days
• Field of Search: 395/750, 123/480, 318/510, 364/431.11, 364/200, 364/900, 365/226, 365/229, 371/9.1, 371/12, 371/16.3
• US Class Current: 713/330
• CPC Class Codes: G06F 1/24 Resetting means
• CPC Class Codes: G06F 1/30 Means for acting in the event of power-supply failure or interruption, e.g. power-supply fluctuations for resetting only G06F1/24
• CPC Class Codes: G06F 1/305 in the event of power-supply fluctuations
• CPC Class Codes: G06F 1/32 Means for saving power

Abstract

A voltage regulator connected to a microcomputer is switched from main power to standby power by a monitoring integrated circuit in response to a switch off by the control circuit after receiving a switch off command, from an ignition switch, and only after the computer has been reset. The monitoring integrated circuit has a plurality of circuit elements including a circuit element which generates a control signal for switching the voltage regulator to a state producing a standby voltage which powers the microprocessor to save the information in the microprocessor memory. Preferably the circuit element generating the control signal is an operational amplifier whose output is fed by a time delay network which delays switching of the voltage regulator.

Claims

1. A power supply arrangement for a microcomputer having an associated random access memory means, comprising a battery, voltage regulator means for producing a regulated main power at a main voltage and a regulated standby power, said voltage regulator means being connected to a microcomputer having a random access memory to supply the regulated main power to the microcomputer when the microcomputer is switched on and the regulated standby power to the microcomputer to retain information in said random access memory when the microcomputer is switched off, and said voltage regulator means having a control input for receiving an "on" signal to switch the voltage regulator means to supply the regulated main power to the microcomputer, said voltage regulator means supplying said regulated standby power when said "on"signal is not present at said control input;

means for providing the "on" signal connected electrically to the control input, said means for providing including an ignition switch;

a monitoring integrated circuit means for producing a resetting signal to the microcomputer connected electrically to the microcomputer, said monitoring integrated circuit means having a monitoring input connected electrically to said means for providing the "on" signal and producing a resetting signal in response to an "on" signal received at said monitoring input;

a time delay network including a capacitor and resistors connected to the monitoring integrated circuit means to maintain the "on" signal at said control input for a time interval after the ignition switch has been switched off to trigger the voltage regulator means to supply the regulated standby power to the microcomputer so that the voltage regulator means continues to supply the regulated main power for the time interval, said time interval being of a sufficient duration so that the microcomputer has reached a defined state in response to the resetting signal produced by the monitoring integrated circuit means before said voltage regulator means switches to provide said regulated standby power to said microcomputer.

2. A power supply arrangement according to claim 1, wherein said monitoring integrated circuit means has a safety input for receiving a self-monitoring signal from the microcomputer to reset the microcomputer when the microcomputer malfunctions.

3. A power supply arrangement for a microcomputer having an associated random access memory means, comprising a battery, voltage regulator means for producing a regulated main power at a main voltage and a regulated standby power, said voltage regulator means being connected to a microcomputer having a random access memory to supply the regulated main power to the microcomputer when the microcomputer is switched on and the regulated standby power to the microcomputer to retain information in said random access memory when the microcomputer is switched off, and said voltage regulator means having a control input for receiving an "on" signal to switch the voltage regulator means to supply the regulated main power to the microcomputer, said voltage regulator means supplying said regulated standby power when said "on" signal is not present at said control input;

means for providing the "on" signal connected electrically to the control input, said means for providing including an ignition switch;

a monitoring integrated circuit means for producing a resetting signal to the microcomputer connected electrically to the microcomputer, said monitoring integrated circuit means having a monitoring input connected electrically to said means for providing the "on" signal and producing a resetting signal in response to an "on" signal received at said monitoring input;

a watchdog circuit for producing the resetting signal, the monitoring integrated circuit means including two operational amplifiers connected electrically in series between the monitoring input and the watchdog circuit so that the resetting signal is generated in response to a change in potential at the monitoring input as a result of receiving the "on" signal; and

a time delay network including a capacitor and resistors connected to the monitoring integrated circuit means to maintain the "on" signal at said control input for a time interval after the ignition switch has been switched off to trigger the voltage regulator means to supply the regulated standby power to the microcomputer so that the voltage regulator means continues to supply the regulated main power for the time interval, said time interval being of a sufficient duration so that the microcomputer has reached a defined state in response to the resetting signal produced by the monitoring integrated circuit means before said voltage regulator means switches to provide said regulated standby power to said microcomputer.

4. A power supply arrangement as defined in claim 3, wherein the time delay network comprises a circuit consisting of the capacitor and one of the resistors, said circuit being connected electrically in series between the control input and the monitoring integrated circuit means.