JPS61214014A - Power supply circuit for microcomputer - Google Patents

Abstract

PURPOSE:To prevent the malfunction of a microcomputer and also to simplify the constitution of a power supply circuit for microcomputer together with the reduction of cost, by keeping the 1st terminal in a state of the power is being supplied at all times and also setting the level of the 2nd terminal at the value lower than the 1st terminal by an amount equal to the voltage drop produced in a conduction mode of a semiconductor switching element. CONSTITUTION:A microcomputer 11 is set to a tuning radio receiver 10 and energized by a DC power supply 12. The electric power is supplied to a basic frequency generating circuit 21 as well as a central controller 25 containing a memory 26 of the computer 11 from the 1st terminal VDD via a line 27. At the same time, the electric power is supplied to other circuits of the computer 11 as well as each circuit of the receiver 10 respectively from the 2nd terminal CE. Then the power supply 12 is connected to the terminal VDD via a stabilizing circuit 29. Furthermore, a switching element consisting of transistors TR 30 and 35 is connected between the terminal CE and the power supply 12. Then the level of the terminal CE is set lower than that of the terminal VDD when both TR 30 and 35 conduct by an amount equal to the voltage drop of said switching element, thus the malfunction of microcomputer 11 is prevented.

Description

TECHNICAL FIELD The present invention relates to a power supply circuit for powering a microcomputer such as in an electronically tuned radio receiver.

Background technology A typical prior art is shown in FIG.

The electric power from the DC type W,1 installed in the automobile is, for example, 13 volts, and is stabilized by being fed from the diode D1 to the stabilizing circuit Q1, and the line! 1 to the first backup terminal VDD of the microcomputer 2. Also, the power from the DC power supply 1 is passed through the switch 3, another stabilizing circuit Q2, the resistor R1, and the line! 2 to the #+2 terminal CE of the microcomputer 2. Capacitors C1-C5 are used for smoothing. line! 1. ! A diode D2 is provided between the two. The memory 4 built into the microcomputer 2 is constantly powered by the power from the first terminal VDD of the microcomputer 2.

When the switch 3 is turned on, the remaining circuits other than the memory 4, which consume relatively large amounts of power, are powered by the power from the second terminal CE, thereby causing the microcomputer 2 to operate.

This microcomputer 2 malfunctions when the voltage of the second ylJ child CE rises by 2'' compared to the voltage of the 11th child VDD. Such malfunctions can occur in the stabilizing circuits Ql, Q
2 may be caused by manufacturing errors. Therefore, it is necessary to take measures to prevent such malfunctions from occurring in the microcomputer.

In addition, the microcomputer mentioned above has the first
If power is supplied to the second terminal CE before the terminals V and DD, a malfunction will occur. Such malfunctions occur especially when the output voltage of the DC power supply 1 decreases, the capacitors C1 and
C2; This may occur due to the capacitance of C3, C4, etc. To solve this problem, resistor R1 and capacitor C5
Which time constant circuit is configured to apply a voltage to the second terminal CE with a delay from the first terminal VDD.

Further, the guide D2 is also provided for the same purpose.

Furthermore, in this prior art, the stabilizing circuit Ql.

Two Q2s are required. As described above, the circuit configuration in the first technology is relatively complicated, and it is desired to reduce the number of parts and cost.

Problems to be Solved by the Invention An object of the present invention is to provide a power supply circuit for a microcomputer with a simple circuit configuration that reliably prevents malfunctions of the microcomputer.

Means for Solving the Problems The present invention provides a power supply circuit for a microcomputer that powers a microcomputer including a memory etc. with power from a DC power supply.
It includes a first terminal for energizing the memory, etc., and a second terminal for energizing the remaining circuits other than the memory, the first terminal is connected to a DC power supply, and the second terminal is connected to a DC power source. A semiconductor switching element is interposed between the DC power supply and the semiconductor switching element, the semiconductor switching element has a control terminal for receiving a control signal for changing the switching mode, and a means for generating the control signal is provided. This is a power supply circuit for a microcomputer.

Effect According to the present invention, by applying a control signal to the control terminal of the semiconductor switching element, this semiconductor switching element is made conductive, thereby causing the first yf11 child to have the second
It is ensured that power is always supplied before the terminal, and the voltage applied to the first terminal is lower than the voltage applied to the second terminal by at least the voltage drop when the semiconductor switching element is conductive. In this way, malfunctions of the microcomputer can be reliably prevented. Moreover, the structure is relatively simple and is excellent in cost reduction.

Embodiment FIG. 1 is an electrical circuit diagram of an embodiment of the present invention. The electronically tuned radio receiver 10 mounted on a motor vehicle has a microcomputer 11, which is powered by a DC power supply 12. The high frequency signal from the antenna 13 is
The intermediate frequency signal is applied to the mixing circuit 14 according to the superhetero gain method, frequency converted, the intermediate frequency signal is amplified in the intermediate frequency amplifier circuit 15, detected in the detection circuit 16, the audio signal is amplified in the amplifier circuit 17, and is output by the speaker 18. It becomes acoustic. The mixing circuit 14 is given a local oscillation frequency signal from a local oscillation circuit 19 including a voltage dependent variable capacitance diode.

In the microcomputer book, a seven-piece electronic loop frequency synthesizer 20 is provided.

This 7-piece Izrolock loop frequency synthesizer 20 is
A fundamental frequency generation circuit 21 , a frequency division circuit 22 that divides this fundamental frequency signal, and a phase comparison circuit 23 that performs a phase comparison between the signal from this frequency division circuit 22 and the local oscillation frequency signal from the local oscillation circuit 19 . and a low-pass filter 24, and the output voltage from the low-pass filter 24 is applied to the voltage-dependent variable capacitance diode of one local oscillation circuit. In this way, the local oscillation frequency (frequency of i) matches the frequency derived from the frequency divider circuit 22 and becomes locked. The frequency division ratio of the frequency divider circuit 22 is determined by the output from the central processing circuit 25. By converting the frequency division ratio of the circuit 22, the local oscillation frequency of the local oscillation circuit 19 changes, thereby changing the tuning frequency.The central processing circuit 25 stores the frequency division ratio of the frequency division circuit 22, etc. The central processing circuit 25 and the fundamental frequency generating circuit 21 are connected to a first backup terminal VDD via a line 27. The power consumption of the generation circuit 21 is relatively small.On the other hand, the second terminal CE l: connected frequency divider circuit 22, phase comparator circuit 2
3. The power consumption of the low-pass filter 24, as well as the mixing circuit 14, the intermediate frequency amplification circuit 15, the detection circuit 16, the amplification circuit 17, and the local oscillation circuit 19 is relatively large. The microcomputer 11 has a second terminal C rather than a first terminal VDD.
It has a characteristic of causing malfunction when the voltage of E increases.

Further, if a voltage is applied to the second terminal CE before the first terminal VDD, the microcomputer 11 has a characteristic that malfunctions occur.

In order to prevent such malfunctions of the microcomputer 11 from occurring, the present invention is configured as follows. The power from the DC power supply 12 is line! 3, passes through the diode D3, is smoothed by the capacitor C6, and is applied to the stabilizing circuit 29. The output voltage of the DC power supply 12 is, for example, 13 volts, which is stepped down to 5 volts by the stabilizing circuit 29, and the line! 4 first terminal VDD
is applied to This line! 4 is connected to a smoothing capacitor C7. line! A PNP transistor 30, which is a semiconductor switching element, is interposed between the line 4 and the line 5 to which the second terminal CE is connected. The collector of transistor 30 is grounded via resistor 31. The saturation voltage between the collector and emitter when the transistor 30 is conductive is, for example, about 0.1 volt, which is a relatively low value.

The power from the DC power supply 12 is passed from the switch 32 through the line nozzle, and from the resistor 33 to the base of the F run raster 35.
available. A resistor 3 is connected to the base of this transistor 35.
6 is connected. In connection with transistor 30.35,
Resistors 37 and 38 are connected. The power from the DC power source 12 via the switch 32 energizes the ignition circuit 39 of the internal combustion engine for driving the vehicle.

In operation, when switch 32 is in the blocking state, transistor 35 is blocking and therefore transistor 30 is also blocking. In this state, the power from the DC power supply 12 is on the line! 3, diode D3, stabilization circuit 29 and line! Power is supplied to the first terminal VDD via 4. Therefore, the memory 2 provided in the processing circuit 25
6 is always powered on, and there is no risk that its stored contents will be erased. The fundamental frequency generating circuit 21 is also energized. The amount of power consumed by the first terminal VDD is small and does not place an excessive load on the DC power supply 12.

When the switch 32 is turned on, the transistor 35 becomes conductive, and in response, a low-level control signal is applied to the base, which is the control terminal, of the transistor 30, thereby making the transformer and the mester 30 conductive. Therefore, the power from the line 4 is applied to the second terminal CE via the transistor 30 and further via the line 5.

This brings the microcomputer 11 into operation, allowing the radio receiver 10 to receive radio broadcasts.

Power from Line No. 4 passes through transistor 30 to Line! 5, the voltage at the second terminal CE is lower than that at the first terminal VDD. This prevents the microcomputer from malfunctioning. Line again! Power from line J?4 is passed through transistor 30 to line J?
5, power is supplied to the second terminal CE at the same time as or later than the first terminal VDD. Therefore, this also makes it possible to
Malfunctions of the data controller 11 are prevented.

Transistor 30 is suitably a PNP type bipolar F transistor. Such a transistor 3° has a collector
the emitter-to-emitter saturation voltage is less than 0.1 volt;
The voltage applied to the second terminal CE is relatively low, so that the microcomputer 11 is prevented from malfunctioning due to an unnecessary drop in the voltage applied to the second terminal CE.

The voltage flowing into the emitter of the transistor 30 is 11, the collector current is 12, the base current is ■3, and the line! When the current flowing through resistor 31 is 14 and the current flowing through resistor 31 is 15, equations (1) and (2) hold true.

I 1 = I 2 + I 3 ... (1) I
2=I 4+I 5 ...(2) Second
If the current I4 supplied to the terminal CE increases unnecessarily, the microcomputer 11 may malfunction. At this time, by appropriately setting the resistance value of the resistor 31, it is possible to adjust the current (4) so that it does not become excessive. Switch, VDD...1st terminal, CE...
- According to this configuration, circuit design becomes easy.

The present invention can be widely implemented in connection with the microcomputer 1 associated with electronic tuned radio reception +9110, as well as other microcomputers.

Effects As described above, according to the present invention, power can always be supplied to the first terminal, and moreover, the second terminal has a lower voltage drop than the first terminal due to the voltage drop when the semiconductor switching element is conductive. Since the current level is at least low, malfunctions of the microcomputer can be reliably prevented. Furthermore, the configuration is relatively simple and is excellent in cost reduction.

[Brief explanation of the drawing]

FIG. 1 is an electrical circuit diagram of one embodiment of the present invention, and FIG. 2 is an electrical circuit diagram of the prior art. 11...microcomputer, 12...if t
lL I! '11.25...Central processing circuit, 26.
...Memory, 29...Stabilization circuit, 30.35-) transistor, 32...Sui agent Patent attorney Number of strokes Keiichi JP-A-61-214 old 4 (5)

Claims (1)

[Claims] In a power supply circuit for a microcomputer that powers a microcomputer including a memory etc. with power from a DC power supply, the microcomputer comprises a first terminal for powering the memory etc.; and a second terminal for energizing the remaining circuits other than the memory etc., the first terminal is connected to a DC power supply, and a semiconductor switching element is interposed between the second terminal and the DC power supply. A power supply circuit for a microcomputer, characterized in that the semiconductor switching element has a control terminal for receiving a control signal for changing a switching mode, and is provided with means for generating the control signal.