TWI407840B - Real time clock driving circuit - Google Patents

Abstract

The present invention relates to a real time clock driving circuit. The real time clock driving circuit is operable for providing electrical source to a Real Time Clock Integrated Circuit (RTC IC) of a camera. The real time clock driving circuit includes a flash circuit, a switch circuit, and a main electrical source. The flash circuit includes a transformer, a flash charging capacitor, and at least one fractional pressure resistances. The switch circuit includes a MOS transistor and a fifth resistance. The main electrical source is electrically coupled to the transformer, the grid of the MOS transistor, and an input end of the RTC IC, respectively. The flash charging capacitor and one end of the at least one fractional pressure resistances are respectively electrically coupled to an output end of the transformer. The other end of the at least one fractional pressure resistances is electrically coupled to the source of the MOS transistor, and electrically coupled to the grid of the MOS transistor via the fifth resistance. The drain of the MOS transistor is electrically coupled to the input end of the RTC IC.

Description

Instant clock drive circuit

The invention relates to an instant clock driving circuit.

Many of the previous electronic devices have a clock timing function to increase their convenience. Digital cameras, mobile phones, and PDAs that are commonly used today require an instant clock integrated circuit to allow the instant clock integrated circuit to continue to maintain timing after the electronic device is turned off. When the power is turned on again, the instantaneous clock product The body circuit can immediately supply the correct timing.

The real-time clock integrated circuit of the digital camera mainly includes a Real Time Clock Integrated Circuit (RTC IC), a main power supply and a gold capacitor. When the main power is turned off, the gold capacitor is charged while the RTC IC is powered. The digital camera is turned off during the replacement of the battery, and the digital camera is powered by a gold capacitor that stores electrical energy in advance to provide operating power for the RTC IC. However, gold capacitors are relatively expensive and provide less time to power the RTC IC.

In view of this, the present invention provides an instant clock driving circuit with long power supply duration and low production cost.

An instant clock driving circuit for providing driving power to an instant clock generator of a digital camera. The instant clock driving circuit includes a flash circuit, a switching circuit and a main power source. The flash circuit includes a transformer, a flash charging capacitor and at least a first voltage dividing resistor. The switching circuit includes a transistor and a second voltage dividing resistor. The main power source is electrically connected to the transformer, the gate of the transistor and the power input end of the instant clock generator. The flash charging capacitor and one of the at least one first voltage dividing resistor are electrically connected to the output end of the transformer, respectively. The other end of the at least one first voltage dividing resistor is electrically connected to the source of the transistor and is electrically connected to the gate of the transistor by the second voltage dividing resistor. The drain of the transistor is electrically connected to the power input of the instant clock generator.

Compared to the prior art, when the main power is turned off, the flash charging capacitor is discharged, the transistor of the switching circuit is turned on, and the flash charging capacitor provides an operating voltage for the instant clock generator. Therefore, there is no need to add additional gold capacitors, the production cost is reduced, and the flash charging capacitor is large, which can provide a long duration of power supply.

100‧‧‧ Instant clock drive circuit

10‧‧‧Flash circuit

20‧‧‧Switch circuit

30‧‧‧Main power supply circuit

40‧‧‧ Instant Clock Generator

11‧‧‧Transformers

50‧‧‧flash

O1‧‧‧ first node

O2‧‧‧ second node

O3‧‧‧ third node

O4‧‧‧ fourth node

110‧‧‧Main power supply

R1‧‧‧first resistance

R2‧‧‧second resistance

R3‧‧‧ third resistor

R4‧‧‧fourth resistor

C1‧‧‧Flash charging capacitor

Q‧‧‧Optocrystal

G‧‧‧Gate

S‧‧‧ source

D‧‧‧Drain

C2‧‧‧Time delay capacitor

R21‧‧‧Second voltage divider resistor

R22‧‧‧ third voltage divider resistor

D1‧‧‧First Diode

D2‧‧‧ second diode

C3‧‧‧Filter Capacitor

12‧‧‧First voltage divider resistor

FIG. 1 is a circuit diagram of an instant clock driving circuit according to an embodiment of the present invention.

The embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

Referring to FIG. 1 , an instant clock driving circuit 100 is provided for driving an instant clock generator 40 of a digital camera, and includes a main power source 110 , a flash circuit 10 , a switch circuit 20 , and a Main power supply circuit 30.

In this embodiment, the main power source 110 is a battery.

The flash circuit 10 includes a transformer 11, at least a first voltage dividing resistor 12 and a flash charging capacitor C1. The main power source 110 is electrically connected to an input end of the transformer 11 . The output end of the transformer 11 is electrically connected to the flash charging capacitor C1. The transformer 11 is configured to output a voltage of 300V to the flash charging capacitor C1 to charge the flash charging capacitor C1. The flash charging capacitor C1 is used to store electrical energy for the flash 50 of the digital camera. The other end of the flash charging capacitor C1 is grounded. A first node O1 is formed between the transformer 11 and the flash charging capacitor C1. In this embodiment, the at least one first voltage dividing resistor 12 includes a first resistor R1, a second resistor R2, a third resistor R3, and a fourth resistor R4. The first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are sequentially connected in series. And the first resistor R1 is connected in series on the first node O1. A second node O2 is formed between the second resistor R2 and the third resistor R3.

The switch circuit 20 includes a transistor Q, a third voltage dividing resistor R22, a second voltage dividing resistor R21, a first diode D1 and a delay capacitor C2. In this embodiment, the transistor Q is a P-MOS transistor. The source S of the transistor Q is electrically connected to the second node O2, and the drain D of the transistor Q is electrically connected to the Real Time Clock Integrated Circuit (RTC IC). The power input. The main power source 110 is electrically connected to the gate G of the transistor Q by the first diode D1. The gate G of the transistor Q and the first diode D1 form a third node O3. One end of the third voltage dividing resistor R22 is electrically connected to the third node O3, and the other end is grounded. The anode of the delay capacitor C2 is electrically connected to the second node O2, and the cathode is electrically connected to the third node O3. Similarly, one end of the second voltage dividing resistor R21 is electrically connected to the second node O2, and the other end is electrically connected. Three nodes O3.

The main power supply circuit 30 includes a second diode D2 and a filter capacitor C3. The main power source 110 is electrically connected to the power input end of the instant clock generator 40 by the second diode D2. A fourth node O4 is formed between the second diode D2 and the power input end of the instant clock generator 40. The anode of the filter capacitor C2 is connected to the fourth node O4, and the cathode is grounded. It can be understood that the flash power circuit 10, the switch circuit 20 and the main power source 110 in the main power supply circuit 30 are the same power source, that is, the battery of the digital camera.

In use, when the battery of the digital camera is powered, that is, when the main power source 110 is powered, the voltage of the main power source 110 boosted by the transformer 11 is 300V, and the flash charging capacitor C1 is charged. At the same time, since the main power source 110 supplies power to the switch circuit 20, the main power source 110 passes through the first diode D1 to supply a voltage to the gate G of the transistor Q, and the voltage of the first node O1 passes through The first resistor R1, the second resistor R2, the third resistor R3, and the fourth resistor R4 are divided to obtain a voltage smaller than the voltage of the main power source 110. Since the gate G voltage is higher than the source S voltage, the transistor Q deadline. The operating voltage of the instant clock generator 40 is provided by the main power supply circuit 30. Specifically, the main power supply 110 in the main power supply circuit 30 supplies the operating voltage to the instant clock generator 40 via the second diode D2. .

When the digital camera replaces the battery, that is, when the main power source 110 has no power, the voltage of the main power source 110 is 0V. At this time, the flash charging capacitor C1 starts to discharge, and passes through the first resistor R1, the second resistor R2, and the third resistor. After R3 and the fourth resistor R4 are divided, a voltage V1 is obtained at the second node O2. In the present embodiment, the voltage V1 is about 3V. At this time, the voltage V1 is applied to the source Q of the transistor Q, and the voltage V1 is subjected to the second partial voltage. The resistor R21 is applied to the gate G of the transistor Q after being divided, and the gate G obtains a voltage of about 0.3 V. Since the gate G voltage is lower than the source S voltage, the transistor Q is turned on. At this time, the operating voltage of the instant clock generator 40 is provided by the flash charging capacitor C1.

When the main power source is disconnected, the flash charging capacitor is discharged, the transistor of the switching circuit is turned on, and the flash charging capacitor provides an operating voltage for the instant clock generator. Therefore, there is no need to add additional gold capacitors, the production cost is reduced, and the flash charging capacitor is large, which can provide a long duration of power supply.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only a preferred embodiment of the present invention, and it is not possible to limit the scope of the patent application of the present invention. Equivalent modifications or variations made by persons skilled in the art in light of the spirit of the invention are intended to be included within the scope of the following claims.

100‧‧‧ Instant clock drive circuit

10‧‧‧Flash circuit

20‧‧‧Switch circuit

30‧‧‧Main power supply circuit

40‧‧‧ Instant Clock Generator

11‧‧‧Transformers

50‧‧‧flash

O1‧‧‧ first node

O2‧‧‧ second node

O3‧‧‧ third node

O4‧‧‧ fourth node

110‧‧‧Main power supply

R1‧‧‧first resistance

R2‧‧‧second resistance

R3‧‧‧ third resistor

R4‧‧‧fourth resistor

C1‧‧‧Flash charging capacitor

Q‧‧‧Optocrystal

G‧‧‧Gate

S‧‧‧ source

D‧‧‧Drain

C2‧‧‧Time delay capacitor

R21‧‧‧Second voltage divider resistor

R22‧‧‧ third voltage divider resistor

D1‧‧‧First Diode

D2‧‧‧ second diode

C3‧‧‧Filter Capacitor

12‧‧‧First voltage divider resistor

Claims (6)

An instant clock driving circuit for providing a driving power to an instant clock generator of a digital camera, wherein the instant clock driving circuit comprises a flash circuit, a switching circuit and a main power source, and the flash circuit comprises a transformer a flash charging capacitor and at least one first voltage dividing resistor, the switching circuit includes a transistor and a second voltage dividing resistor, the main power source is electrically connected to the transformer, the gate of the transistor and the instant The power input terminal of the clock generator, the flash charging capacitor and the at least one first voltage dividing resistor are respectively electrically connected to the output end of the transformer, and the other end of the at least one first voltage dividing resistor is electrically connected The source of the transistor is electrically connected to the gate of the transistor by the second voltage dividing resistor, and the drain of the transistor is electrically connected to the power input end of the instant clock generator. When the main power source is powered, the output voltage of the main power source is boosted by the transformer to charge the flash charging capacitor, and the charged charging capacitor is one. The light lamp provides a working power source, the main power source provides an operating voltage for the instant clock generator, and when the main power source is turned off, the flash charging capacitor is discharged, and the partial voltage dividing resistor is divided by the at least one first voltage dividing resistor The transistor of the switching circuit is turned on, and the flash charging capacitor is further configured to provide an operating voltage to the instant clock generator. The instant clock driving circuit of claim 1, wherein the at least one first voltage dividing resistor comprises a first resistor, a second resistor, a third resistor, and a fourth resistor, the transformer A first node is formed between the flash capacitor and the first resistor, the second resistor, the third resistor, and the fourth resistor are connected in series, and the first resistor is connected in series at the first node. The instant clock driving circuit of claim 2, wherein a second node is formed between the second resistor and the third resistor, the switch circuit includes a third voltage dividing resistor, a first a diode, a source of the transistor is electrically connected to the second node, and a drain of the transistor is electrically connected to a power input end of the instant clock generator, the main power source Connecting to a gate of the transistor, a gate of the transistor is formed with a third node of the first diode, and one end of the third voltage dividing resistor is electrically connected to the third junction Point, the other end is grounded. The instant clock driving circuit of claim 3, wherein the switching circuit further comprises a delay capacitor, the anode of the delay capacitor is electrically connected to the second node, and the anode is electrically connected to the third Node. The instant clock driving circuit of claim 1, wherein the instant clock driving circuit further comprises a main power supply circuit, the main power supply circuit comprising a second diode and a filter capacitor, the main The power source is electrically connected to the power input end of the instant clock generator by the second diode, and a fourth junction is formed between the second diode and the power input end of the instant clock generator. Point, the anode of the filter capacitor is connected to the fourth node, and the cathode is grounded. The instant clock driving circuit of claim 1, wherein the transistor is a P-MOS transistor.