JPS63256003A - Oscillation device - Google Patents

Abstract

PURPOSE:To decrease the loss of power by a CR timer as a conventional oscillator by using a microcomputer so as to detect the oscillating state of an oscillation means and selecting a power voltage or a voltage of a voltage drop means depending on the detected oscillating state so as to supply the selected voltage to the oscillating means. CONSTITUTION:A CPU 23 acts like controlling the entire electronic camera as well as detecting the oscillation stop. A latch 26 takes either set or reset state at application of power. In this case, when the latch 26 is reset, a p- channel MOS FET 20 is turned on and power is supplied from a lithium battery VLi to an oscillator 1 and a frequency divider 6 to initiate the oscillation, In confirming the oscillation, the CPU 23 sets the latch 26 is set to turn off the p-channel MOS FET 20 thereby turning on an analog switch 19 instead. After the CPU 23 sets the latch 26, the oscillator 1 and the frequency divider 6 are operated by a voltage being nearly a half the voltage of the VLi. That is, the power voltage is halved to be VLi/2 thereby decreasing the power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oscillation device, and particularly to an oscillation device that requires low power consumption.

[Conventional technology]

Conventionally, this type of apparatus has been constructed as shown in FIG. These circuits are usually all composed of C-MOS circuits to achieve low power consumption, but in C-MOS circuits, the current consumption is proportional to the circuit's operating frequency, so in (a) most of the power is It is consumed in the parts that move at high speed in the circuit, that is, the first few stages of the oscillator 101 and the frequency divider 102, and the entire circuit including this part and the clock part 103 is driven by battery voltage (a) had the disadvantage of high power consumption.

In addition, (b) of the same figure was devised to compensate for the shortcomings of (a), and the oscillator 101 and the first several stages 102 of the frequency divider, which consume most of the power in (a), This is intended to reduce power consumption by driving the converter with a low voltage generated by the step-down circuit 105.

The step-down circuit 105 used here generates a low voltage by switching a capacitor according to timing generated from a clock obtained from an oscillator output, and is a so-called charge pump circuit. Therefore, a switching circuit 110 is required to detect the oscillation stop in order to start oscillation by the oscillation stop detection circuit 107, and to apply the battery voltage itself to the oscillator when the oscillation is stopped.

[Problem that the invention is trying to solve] However,
In the conventional oscillation device, CR is used as the oscillation stop detection circuit 107.
Because a time-limited circuit was used, large values of R and C were required, and these were difficult to manufacture inside the IC, and the external components were either components, or even if they could be integrated inside the IC, they would not be integrated into the chip. This has the drawback that it requires a large area within the battery and also consumes current for charging and discharging the CR.

The primary purpose of the present invention is to eliminate such drawbacks.

[Means for solving problems]

In order to solve the above-mentioned problems, the oscillation device of the present invention provides a means for supplying a power supply voltage, an oscillation means including an oscillation source and a frequency dividing circuit, and a step-down means for lowering the power supply voltage using the oscillation output of the oscillation means. , a microcomputer that selectively detects the oscillation state of the oscillation means for the supplying means and the voltage of the step-down means, and a microcomputer that controls the switching means according to the detected oscillation state.

[For production]

In the above configuration, the switching means is appropriately controlled according to the oscillation state detected by the microcomputer.

〔Example〕

FIG. 1 shows an embodiment of the present invention. Although this embodiment shows an example in which the present invention is applied to an electronic still camera, it is needless to say that the present invention is not limited to this.

In this embodiment, the power supply (Vcc) 3 for the CPU and the lithium battery (VLl) as the power supply for other circuits are independent, and the power supply to the CPU 23 is controlled by the switch 24.

FIG. 2 shows in detail the parts of FIG. 1 that are closely related to the present invention. In FIG. 1, the CPU 23 is
It has the role of not only detecting oscillation stoppage but also controlling the entire electronic camera, that is, the signal processing circuit 27, the disk drive 28, the watch calendar part 9, and other circuits. The configuration and operation of this embodiment will be described below with reference to FIGS. 1 and 2. When the lithium battery 2 is removed, the oscillator 1 naturally stops oscillating, and the step-down circuit 105 does not generate any voltage. When the lithium battery 2 is loaded, the state of the latch 26 becomes undefined. That is, the latch 26 can take either a set or reset state when the power is turned on. At this time, if the latch 26 is reset, p-ch M
OS FET20 turns on and V is applied to oscillator 1 and frequency divider 6.
Li is supplied and oscillation starts. If oscillation does not start, the user turns on the switch 25 to issue a command to the CPU 23 to reset the latch 26.The generated clock is divided by the frequency divider 6 and then transferred to the level shifter 7 (in this case, (The level shifter 7 does not play any role) and enters the step-down circuit. This step-down circuit is a so-called charge pump circuit, and is shown in Fig. 3 a), b).
,c).

FET switches 13°, 14. in response to the pulses shown in d).
By switching capacitors 15 and 16, the capacitors 17 and 18 are sometimes connected in series and sometimes connected in parallel, thereby generating a voltage 1/2 of VLi. This situation is shown in Figure 3e). When the CPU 23 confirms this oscillation, it sets the latch 26 and p-ChFE
T20 is set to 0FFL, and the analog switch 19 is turned on instead. At the time of this switching, both 20 and 19 are O
Since there may be a time when it becomes an FF, an LPF is formed by the resistor 21 and the capacitor 22 to prevent instantaneous interruption. After the CPU 23 sets the latch 26, the oscillator 1 and the frequency divider 6 will operate at a voltage that is half of VLi.

Thereafter, since the output level of the frequency divider 6 is only half of VLi, the output level is returned to the level of VLi by the level shifter 7, and then supplied to the step-down circuit and the clock 9.

In addition, since the CPU 23 is a CPU that also controls the entire electronic camera, there is a switch 4.5 (corresponding to a switch that detects the first press and second press of the release button) as shown in Figure 1. The oscillation is checked every time the button ( ) is pressed.

Next, the operation of the CPU 23 shown in FIGS. 1 and 2 will be explained using the flowchart shown in FIG. 4.

When the power supply voltage is supplied to the CPU 23 by the switch 24, the CPU 23 first latches the level of the boat PO connected to the output of the level shifter 7 as LPO (5102).
), wait 240 μsec (S102). Here, it is assumed that the output of the level shifter 7 operates at 2 kHz combined by the frequency divider 6 while oscillation is occurring.

Therefore, in the oscillating state, the output of the level shifter 7 becomes a square wave with one period of 500 μsec. 51
After the waiting time of 02 has elapsed, the state of the boat Po is latched again to LP1 (S103), and it is determined whether the LP latched in 5101 is reversed, and if it is not reversed, the state is waited for 20 μsec (S105). ), then latch the state of the boat po again and set it as LP2. 106) LP
, , determine whether LP2 are inverted with each other (S1
07). If it is not reversed, it is determined that the excavation of the oscillator 1 has stopped, and the FET (switch) 20 to the latch 26 is turned on. As a result, the lithium voltage VLi is supplied to the oscillator 1 and excavation is started.

Next, depending on the case of the CPU 23, the FET (switch 20
) is set high to indicate that it is turned on.

In addition, when it is detected that the signal is inverted in 5104 and 5107, it is first detected whether the flag is high (5ilo), and if the flag is high, the clock is counted for about 1 second. Start the timer with the time (5 ill), and if the flag is high, jump to 5111 0 Next, if another CPU 23 performs routine processing of the sequence, determine whether it is an end sequence or not 5114 ), if it is an end sequence, go to end, if it is not an end sequence, perform other routine processing (S116), and determine whether the timer shown in 5ill has been completed or the flag has been reset (311B), When the timer timing is completed or the flag is reset, it is assumed that the oscillation of the oscillator 1 has become sufficiently stable, and a command to turn off the FET (switch) 20 and turn on the analog switch 19 is latched. 26 is sent out and supplied to the oscillator 1° frequency divider 6. Power consumption is reduced by setting the power supply voltage to V L i /2.

In this embodiment, the CPU 23 controls the FET (switch) 2.
When 0 is turned on, VLi is applied to the oscillator for a certain period of time by the timer shown in step 5111, so that startup is possible with certainty.

Next, switch 4 and switch 5 switch from OFF to ON1,
When m switching is detected in steps 5122 and 5124, the process returns to step 5101 to check that oscillation is occurring.

3') Check number 1 is always necessary, and 5
The flow may be jumped from 122, 5124 to 5116.

Although the present embodiment discloses an oscillation device used as an oscillation source for the clock calendar part 9, the present invention is not limited to this, and may be used in other devices such as an oscillation device used in an LCD driver. It is clear that the application is not limited.

As explained above, according to this embodiment, the CPU is used to detect oscillation stop and switch the oscillator voltage at the start of excavation.
In the case of U, there is no need to take the trouble to provide an excavation stop detection circuit as shown in the conventional example of FIG. , since the CPU only needs to operate when necessary, the fourth
It is also possible to eliminate the current loss caused by the CR timer, which is generally taken as shown in FIG.

(Effects of the Invention) As explained above, according to the present invention, the oscillation state of the oscillation means is detected by a microcomputer, and the power supply voltage or the voltage of the step-down means is selected according to the detected oscillation state, and the oscillation means Since it is designed to supply C
Power loss due to the R timer can be reduced.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the configuration of an electronic camera to which the present invention is applied, Fig. 2 is a block diagram showing details of Fig. 1, and Fig. 3 is a block diagram showing the details of Fig. 1.
The figure is a timing chart explaining the operation of each circuit in FIG. 2, and FIG. 4 is the same as in FIG. 1. FIG. 2 is a flowchart showing the operation of the CPU shown in FIG. 2, and FIG. 5 is a diagram showing the configuration of a conventional device. DESCRIPTION OF SYMBOLS 1... Oscillator, 2... Lithium battery, 3... Main battery, 4... Release first stroke switch, 5
... Release second stroke switch, 6... Frequency divider, 7... Level shifter, 8... 1/2 frequency divider, 9
...Clock, calendar, 10...NAND gate, 1
1 ・N OR gate, 12 ・N OT gate, 13
．． 14,15.16...Analog switch, 17.1
8... Capacitor, 19.20... Analog switch, 21... Resistor, 22... Capacitor, 23...
・CPU, 24... Main power switch, 25...
・Clock setting switch, 26...Latch, 27...Electronic camera signal processing circuit, 28...Electronic camera disk drive

Claims (2)

[Claims] (1) means for supplying a power supply voltage; oscillation means including an oscillation source and a frequency dividing circuit; step-down means for stepping down the power supply voltage using the oscillation output of the oscillation means; An oscillation device comprising: a switching means for selectively applying the voltage to the oscillation means; a microcomputer that detects an oscillation state of the oscillation means, and a microcomputer that controls the switching means according to the detected oscillation state. (2) The oscillation device according to claim 1, wherein the step-down means is a charge pump circuit that steps down the power supply voltage using the oscillation output of the oscillation means.