JPS6216044B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a low power consumption oscillator circuit built into a battery-driven electronic watch or desktop electronic computer, and particularly relates to a complementary field effect transistor (hereinafter referred to as C-MOST). Regarding the oscillation circuit used.

Generally, the oscillation circuit used in electronic watches etc.
As shown in the figure, a C-MOST 1 consisting of an N-channel field effect transistor (hereinafter referred to as N-MOST) Tr ₁ and a P-channel field effect transistor (hereinafter referred to as P-MOST) Tr ₂ , a crystal oscillator 2, and an oscillation capacitor 3, 4, bias resistor 5, and resistors 6, 7, and the output of C-MOST1 is output as an oscillation signal. The power consumption of this oscillation circuit is expressed as the sum of the through current when C-MOST1 is inverted and the current charging and discharging the oscillation capacitor 3. However, since most of the through current is a reactive current, the resistors 6 and 7 are - Connected in series to MOST1 to limit the current. The relationship between the oscillation current and the value Rs of the resistors 6 and 7 is shown in FIG. 2, and in order to reduce the oscillation current, the value Rs of the resistors 6 and 7 can be increased. However, as Rs increases, the gain of C-MOST1 decreases, and the oscillation start voltage and oscillation stop voltage increase, as shown in FIG. Therefore, if the voltage applied to the oscillation circuit is 1.5V, Rs must be made smaller than _R1 in order to cause the oscillation circuit to oscillate. Furthermore, once oscillation has started, Rs can be increased to _R2 , at which oscillation stops at 1.5V, so in a steady state, an unnecessary current flows, increasing power consumption.

The present invention has been made in view of the above-mentioned points, and provides an oscillation circuit that completely eliminates the conventional drawbacks. The present invention will be described in detail below with reference to the drawings.

FIG. 4 is a circuit diagram showing an embodiment of the present invention,
C- consisting of N-MOSTTr ₁ and P-MOSTTr ₂
MOST8, crystal oscillator 9 forming a crystal π-type circuit, oscillation capacitors 10, 11, C-MOST8
a bias resistor 12 biasing the output of the C-MOST to the midpoint, that is, 1/2 Vss ₁ , resistors 13 and 14 connected in series to the C-MOST8, and N-MOST15 and P- connected in parallel to the resistors 13 and 14, respectively. MOST
An oscillation section is formed by C--
A frequency divider circuit 17 that divides the output of MOST 8, that is, an oscillation output, into a desired frequency, a booster circuit 20 that boosts the voltage using capacitors 18 and 19 using the divided frequency, the boosted voltage Vss ₂ , and a battery 21
Input the voltage Vss ₁ of P-MOST16 and N
- It is composed of a detection circuit 22 and an inverter 23 that control the MOST 15.

The voltage of the battery 21, that is, Vss ₁ , is -1.5V, and C
- The MOST 8, frequency divider circuit 17, booster circuit 20, and detection circuit 22 are driven by this voltage. C
- The value Rs of the resistors 13 and 14 connected in series with the MOST 8 is located between R ₁ and R ₂ from the characteristic diagram shown in FIG.

That is, when a voltage of -1.5V is applied, oscillation does not start as it is, but once oscillation has started, the value is large enough to continue oscillation. N-MOST15 connected in parallel to these resistors 13 and 14
And the P-MOST 16 serves to start oscillation when the battery 21 is applied. More specifically, since oscillation has not started when the battery 21 is applied, no output is output from the frequency dividing circuit 17, and the boosting operation of the boosting circuit 20 remains stopped. Therefore, no voltage is generated at the boosted output _Vss2 .
At this time, the detection circuit 22 detects that no voltage is generated at Vss ₂ , that is, that oscillation has not started, and sets its output to the Vss ₁ level. Therefore, P-
A Vss ₁ level voltage is applied to the gate of the MOST 16, a “0” level voltage is applied to the gate of the N-MOST 15 via the inverter 23,
Both N-MOST 15 and P-MOST 16 become conductive. In other words, the resistors 13 and 14 are short-circuited, and the C-MOST 8 is essentially connected to the resistor 1.
3 and 14 are not connected, and C-
MOST8 immediately starts oscillating at a voltage of -1.5V. When oscillation starts, the divided frequency is output from the output of the frequency divider circuit 17, and the booster circuit 20
starts working. Therefore, the boosted output Vss ₂ rises to twice the voltage Vss ₁ of the battery 21, that is, -3.0V. At this time, the voltage Vss ₁ of the battery 21 and the boost output
The detection circuit 22 to which Vss ₂ is input has a boosted output
When Vss ₂ becomes greater than Vss ₁ , C-MOST
It is detected that the oscillation of 8 has reached a steady state, and in order to cut off the conductive P-MOST 16 and N-MOST 15, the output is changed from the Vss ₁ level to the "0" level. Therefore, since P-MOST16 and N-MOST15 are blocked, C-MOST8
The resistors 13 and 14 are connected in series. The value Rs of these resistors 13 and 14 is as described above.
Since R ₁ <Rs <R ₂ , the oscillation of C-MOST 8 is sustained. And the resistors 13 and 14 are C-
Since it acts as a limiting resistor that allows only the current necessary to sustain MOST8 oscillation to flow, power consumption can be extremely reduced.

The oscillation circuit shown in this example is mainly used for electronic watches or desktop electronic computers that use a liquid crystal display board, and in addition to 1.5V circuits driven by 1.5V, these oscillation circuits are It has 3.0V circuits such as driving circuits and counting circuits.
A boosted voltage Vss ₂ is required to drive the 3.0V circuit. Further, when a battery having an electromotive force of 3.0V, for example a lithium battery, is used, a step-up circuit is not necessary, but a step-down circuit is required.

It is clear that the present invention can be used in the oscillation circuit in this case as well.

As described above, according to the present invention, P-MOST or N-
By connecting the MOSTs in parallel and shorting the resistor to start oscillation when the battery is applied, the oscillation current flowing to the C-MOST is limited by the resistor after oscillation starts, greatly reducing power consumption. The effect is particularly great when used in electronic watches or desktop electronic computers.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing a conventional example, Figure 2 is a characteristic diagram showing the relationship between resistance and oscillation current, Figure 3 is a characteristic diagram showing the relationship between resistance and oscillation start voltage and oscillation stop voltage. 1 is a circuit diagram showing an embodiment of the present invention. FIG. 8...C-MOST, 9...Crystal resonator, 10,1
1...Oscillation capacitor, 12...Bias resistor, 1
3, 14...Resistance, 15...N-MOST, 16...P
- MOST, 17... Frequency divider circuit, 18, 19... Capacitor, 20... Boost circuit, 21... Battery, 22... Detection circuit, 23... Inverter.

Claims (1)

[Claims] 1. In an oscillation circuit consisting of a complementary field effect transistor, a crystal oscillator, and a capacitor, at least one resistor connected in series with the complementary field effect transistor, and a field effect transistor connected in parallel with the resistor. A transistor, a circuit that steps up or steps down a power supply voltage based on an oscillation output, and a detection circuit that detects generation of the step-up output or step-down output of the circuit, and controls the field effect transistor by the detection output of the detection circuit. An oscillation circuit characterized by: