JPH0543226U - In-vehicle micro computer power supply circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a power supply circuit for a vehicle-mounted microcomputer in which unnecessary current does not flow in the sleep mode of the microcomputer. [Configuration] During normal operation of the microcomputer 1, the transistors 9 and 8 are turned on by the Q output of the latch circuit 5, and a voltage of 5 V from the power supply circuit 3 is applied to the microcomputer 1. When the microcomputer 1 enters the sleep mode due to the end of operation of the vehicle, the latch circuit 5 is reset, the transistors 9 and 8 are turned off, and the voltage of 5V is lowered to 3V by the voltage drop circuit 7, so that useless current is suppressed. [Effect] The current in the sleep mode is reduced, and the battery lasts longer.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a power supply circuit for an in-vehicle microcomputer that supplies power to a microcomputer mounted in an automobile or the like.

[0002]

[Prior Art]

 2. Description of the Related Art As a power supply circuit for a conventional vehicle-mounted microcomputer, for example, there is one as shown in FIG. In the figure, 1 is a microcomputer (hereinafter referred to as a microcomputer), 2 is an on-vehicle battery, 3 is a power supply circuit that stabilizes the voltage of the on-vehicle battery 2 to a voltage of 5 V, and supplies the voltage to the microcomputer 1 and peripheral parts, and 4 is a microcomputer. This is an interrupt input for operating 1 as an interrupt.

Next, the operation will be described. In a normal operation state (active mode) such as when the vehicle is operating, the power supply circuit 3 converts the voltage of the battery 2 into a voltage of 5V and stabilizes it, and then supplies it to the microcomputer 1 as a power supply voltage. The microcomputer 1 performs a predetermined control process for vehicle operation.

When the operation of the vehicle is finished and, for example, the engine is stopped, the door is locked, etc., the microcomputer 1 is switched to a sleep mode in which the clock is stopped and functions other than the interrupt function are stopped.

In the sleep mode, for example, when the door knob is operated or the door is unlocked to start the operation of the vehicle, the interrupt input 4 is added. As a result, the microcomputer 1 is released from the sleep mode and is switched to the active mode again.

[0006]

[Problems to be solved by the device]

 However, in such a conventional power supply circuit for a vehicle-mounted microcomputer, the power supply circuit 3 normally applies a power supply voltage of 5V to the microcomputer 1 and its peripheral parts even when the microcomputer 1 enters the sleep mode. Therefore, there is a problem that useless current consumption flows and the life of the battery 2 is shortened.

The present invention has been made in view of such a conventional problem, and when the microcomputer is in the sleep mode, the power supply voltage supplied to the microcomputer and peripheral parts is lowered. Therefore, it is intended to solve the above problems.

[0008]

[Means for Solving the Problems]

 In this invention, when the microcomputer 1 enters the sleep mode, the power supply voltage is lowered to a low level where only the interrupt function can operate, and when the interrupt input switches the active mode, the power supply voltage is set to the normal level. A power supply control means for resetting is provided.

[0009]

[Action]

 In sleep mode, a low power supply voltage is applied to the microcomputer, so no wasted current is consumed, and the interrupt function is retained, enabling a return to active mode.

[0010]

【Example】

 The invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of this invention. First, the structure will be described. Reference numeral 5 is a latch circuit composed of a D-type flip-flop or the like. The output voltage of the power supply circuit 3 is applied to its D terminal and the interrupt input 4 is applied to its clock terminal C. Further, a reset signal 6 as a control signal is applied to the reset terminal R from the microcomputer 1.

Reference numeral 7 is a voltage drop circuit for reducing the output voltage of the power supply circuit 3, which is composed of a series circuit of three diodes, and the output voltage is applied to the microcomputer 1 as a power supply voltage. Reference numeral 8 is a voltage switching transistor connected in parallel with the voltage drop circuit 7, 9 is a control transistor for controlling the Q output of the latch circuit 5, and the collector output of the transistor 8 controls the transistor 8. Has been done. Reference numeral 10 is a power supply switching circuit composed of transistors 8 and 9. The latch circuit 5, the voltage drop circuit 7, and the power supply switching circuit 10 constitute a power supply control means.

Next, the operation will be described. When the microcomputer 1 is in the sleep mode, the Q output of the latch circuit 5 is "L" (low level), so that both the transistors 9 and 8 are off. Therefore, the 5V output voltage of the power supply circuit 3 is lowered by the voltage drop circuit 7 by the threshold voltage of three diodes, and becomes a voltage of about 3V and is supplied to the microcomputer 1 and the peripheral portion.

As a result, the other functions of the microcomputer 1 are stopped while only the interrupt function is held. In this state, since the power supply voltage supplied to the microcomputer 1 and the peripheral portion is low, it is possible to suppress unnecessary current consumption.

Next, in the sleep mode, the interrupt input 4 is generated when the door knob is operated or the door is unlocked to start the operation of the vehicle. As a result, the microcomputer 1 is released from the sleep mode, the latch circuit 5 is operated, and the output voltage of the power supply circuit 3 is read. Therefore, the Q output of the latch circuit 5 is inverted from "L" to "H" (high level), and the transistors 9 and 8 are turned on.

As a result, the output voltage of 5 V of the power supply circuit 3 is supplied to the microcomputer 1 via the transistor 8 as it is, the microcomputer 1 is switched to the active mode, and a predetermined normal operation is performed.

Next, when the operation of the vehicle is finished and the microcomputer 1 is switched to the sleep mode again, the reset signal 6 is generated from the microcomputer 1 immediately before the switching and the latch circuit 5 is reset. Therefore, the Q output becomes "L" again and the transistors 9 and 8 are turned off again. Therefore, the output voltage of the power supply circuit 3 is again reduced to about 3 V by the voltage drop circuit 7 and applied to the microcomputer 1. As a result, the microcomputer 1 enters the sleep mode which maintains the interrupt function.

A low power consumption type circuit can be configured by using a CMOS transistor for the detection circuit of the interrupt input 4.

[0018]

[Effect of the device]

 As described above, according to the present invention, since the power supply voltage is lowered to a level at which the interrupt function can operate in the sleep mode of the microcomputer, the consumption of the microcomputer and peripheral parts in the sleep mode is reduced. The effect is that the current can be reduced and the battery life can be extended.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a power supply circuit of a vehicle-mounted microcomputer according to an embodiment of the present invention.

FIG. 2 is a configuration diagram showing a power supply circuit of a conventional vehicle-mounted microcomputer.

[Explanation of symbols]

 1 Microcomputer 2 Car Battery 3 Power Supply Circuit 4 Interrupt Input 5 Latch Circuit 6 Reset Signal (Control Signal) 7 Voltage Drop Circuit 10 Power Supply Switching Circuit

Claims (1)

[Scope of utility model registration request] 1. When the operation of the vehicle is completed, the sleep mode is switched to a function in which functions other than the interrupt function are stopped. At the start of the operation of the vehicle, the sleep mode is switched to an active mode in which normal operation is possible. In a power supply circuit of a vehicle-mounted microcomputer that is provided with a power supply circuit that is driven by a vehicle-mounted battery and supplies power to the microcomputer, and outputs from the microcomputer immediately before switching from the active mode to the sleep mode. When the supply voltage from the power supply circuit to the microcomputer is reduced to a level at which the interrupt function can operate based on the control signal and the microcomputer is switched from the sleep mode to the active mode. 2. A power supply circuit for a vehicle-mounted microcomputer, comprising power supply control means for returning the voltage supplied from the power supply circuit to the microcomputer to a normal operation level based on the input interrupt input.