JP3461214B2 - DC / DC converter - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a DC / DC converter used in an electronic device using a battery as a power source, such as a camera.

[0002]

2. Description of the Related Art A camera is an electronic device using a battery, and consumes almost no power such as a mode in which a relatively high power consumption is used when operating an operating member and only an LCD display is continued. Have a mode. In the former mode, almost all electric power is supplied to the electronic circuit in the camera, but in the latter mode, electric power is supplied only to the IC having the function of the switch detection circuit for sensing the input of the LCD display or the operation member. Often The reason is that the camera is a product that uses batteries, and in order to cope with the fact that it is left alone without taking a picture for a very long time, it is in a mode with extremely low current consumption in the left state. It's working.

Therefore, as shown in FIG. 1, a display unit DISP which is always supplied with power, a CMOS microcomputer IC1 to which a switch group SW is connected, and an analog processing IC2 which is supplied with power when necessary. It is configured.

The microcomputer IC1 is provided with a low frequency oscillator OSC1 of about 32 KHz and a high frequency oscillator OSC2 for performing a release sequence and calculation at high speed, and a switch for detecting the open / close state of a release button or a back lid of a camera. Display unit DI for displaying group SW, number of film frames, etc.
SP is connected.

In the low current consumption mode, the microcomputer IC1 generally stops the high frequency oscillator OSC2 and operates only the low frequency oscillator OSC1 to operate the display DISP in order to reduce the current consumption from the power input terminal VDD1 as much as possible. Display and switch switch group SW in SL
It is EEP and HALT. Alternatively, the switch group SW is regularly scanned using a timer interrupt.

When there is an input from the switch group SW, the DC / DC control terminal PWON is turned on and the DC / D
The C converter 1 is activated. When the DC / DC converter 1 is activated, power is supplied to the power input terminal VDD2 of the analog processing IC2, and the microcomputer IC1 activates the high-frequency oscillator OSC2 to transfer signals between the microcomputer IC1 and the analog processing IC2. Begins. A photometric sensor SPC is connected to the analog processing IC 2, and the microcomputer IC 1 performs A / D conversion of the signal to control an aperture and a shutter (not shown).

The DC / DC converter 1 receives the battery voltage V _BAT as an input and is supplied with power from the input terminal V _in . And the output V controlled by the control terminal CTRL
It has two outputs, _OUT2 and an output V _OUT1 which is always controlled and cannot be controlled. The output V _OUT1 is the microcomputer IC
1 is input to the power input terminal VDD1 and the output V _OUT2 is connected to the power input terminal VDD2 of the analog processing IC2. For convenience of explanation, or merely represent the outputs V _OUT1, V _OUT2, it may be expressed as an output terminal.

In FIG. 1, the analog processing IC 2 is taken as an example of the load of the output V _OUT2 of the DC / DC converter 1, but this is generally because an analog IC uses a large amount of bias current of an amplifier or the like in its internal circuit. This is because the current consumption is relatively large. Therefore, not only the analog processing IC but also a logic IC using a bipolar element or the like is laid out as the load of the output V _OUT2 .

Since the DC / DC converter 1 of FIG. 1 relates to an embodiment of the present invention, details other than the above-mentioned parts will be described later.

The DC / DC converter 2 shown in FIG. 2 is a conventional example having the same input / output terminals as the DC / DC converter 1 described above. As a conventional example, there is a similar example in US Pat. No. 5,032,864.

First, the converter 2 according to the conventional example shown in FIG. 2 will be described.

The DC / DC converter 2 includes a converter CKT2 using a transformer and a CMOS regulating I.
Control terminal CTRL, consisting of a circuit in which C6 is connected in parallel
Is L ₀ (meaning low level), the transistor Q5 is turned off, and the DC / DC converter control IC5
Since the control terminal / EN of is set to Hi (meaning high level), the switching transistor Q6 is turned off and released, and the energy transfer from the primary to the secondary by the transformer T1 is stopped.

On the contrary, when the control terminal CTRL becomes Hi,
Transistor Q5 turns on and control terminal / E
Since N becomes L ₀ , the IC 5 starts operating. This IC
Reference numeral 5 is a bipolar DC / DC converter control IC, such as "MB3776A manufactured by Fujitsu Limited".

A signal obtained by dividing the output voltage from the output voltage monitoring resistors R3 and R4 is fed back to the feedback terminal F of the IC5.
The output terminal OUT for inputting to B and comparing with the comparator in the IC5 and stabilizing the output voltage to a predetermined value.
Feedback control of the switching duty of.

The transistor Q6 is an output terminal OU of the IC5.
Upon receiving the signal of T, the primary side coil of the transformer T1 is switched, and the energy is transmitted to the secondary side. Transformer T
A Schottky diode SBD3 is connected to the secondary side of 1, where AC is converted to DC, and ripples, spikes, etc. are removed by the next smoothing capacitor C4. The input voltage Vin is supplied to the power supply VCC of the IC5, and when the control terminal / EN is Hi, the IC5 consumes almost no current. The capacitor C3 is a capacitor for stabilizing the voltage on the primary side of the transformer T1.

The CMOS regulation IC 6 receives power from the battery voltage V _BAT and outputs a constant voltage output. When the control terminal CTRL is L _O , the converter CKT2 is off, so no voltage is generated at the output terminal V _OUT2 , and at the output terminal V _OUT1 from the regulating IC6,
The voltage is supplied through the Schottky diode SBD4. On the other hand, when the control terminal CTRL is Hi, the output of the converter CKT2 is the Schottky diode SBD6.
Output to the output terminal V _OUT2 through the output terminal V _OUT1
Is supplied with the higher potential of the converter CKT2 or IC6 through the Schottky diode SBD4 or SBD5.

Generally, many electric circuits use a power source of around 5V. Further, _assuming that the battery voltage V _BAT is around 6 V, which is around four manganese batteries, the battery voltage V _BAT greatly fluctuates from 2 V to 7 V when an unillustrated motor or strobe circuit operates.

Schottky diodes SBD5, SBD
If the voltage drop of 6 is 0.4 V, the converter CKT
The ratio of the resistance values of the resistors R3 and R4 is set so that the output of 2 becomes 5.4V. When the regulating IC 6 outputs 5V, the output V _OUT1 , V _OUT2 from the converter CKT2 when the load in which the DC / DC converter 2 is on is large.
In both cases, an output of about 5V is obtained. On the other hand, when the DC / DC converter 2 is off, the regulation IC 6
Output through SBD4 Only V _OUT1 "5-0.4 = 4.6
V "is supplied. When DC / DC is off, CKT2
Has almost no current consumption, and since IC6 is a CMOS type, microcomputer IC1 connected to output terminal V _OUT1
Is a light load, the current supplied from the battery voltage V _BAT can be made extremely small.

On the other hand, when the DC / DC converter 1 is on, the outputs V _OUT1 and V _OUT2 can be made to have substantially the same potential, so that IC1
Even if signals are exchanged between the IC2 and the IC2, there is no fear that the signal current leaks to the power supply side through the protection diode or the like on the power supply side set in the input / output terminals of each IC.

[0020]

However, the conventional example has the following problems because the transformer is used for the DC / DC converter.

1) The primary and secondary couplings of the transformer are very important, and the efficiency cannot be improved so much.

2) Since the transformer requires many terminals,
It is expensive to implement.

3) Transformers are relatively expensive.

From the above, a circuit that replaces FIG. 2 without using a transformer has been desired.

(Object of the Invention) An object of the present invention is to replace the transformer with an inductor which is advantageous in terms of cost, size, performance and the like, and consumes the battery voltage in the standby state of the connected electronic circuit. It is to provide a DC / DC converter that can make the voltage extremely small.

[0026]

In order to achieve the above object, the present invention according to claim 1 is such that an inductor connecting one terminal to one terminal of a power source and an inductor connected to the other terminal of the inductor are connected. A diode, a switching element in which one electrode is connected to the connection point of the inductor and the diode and the other electrode is connected to the other terminal of the power supply, and the voltage of the other terminal of the inductor is constantly output.
An output terminal for said diode is branched and connected to a connection line connecting said output terminal, an output voltage detecting means for detecting the voltage boosted by said inductor, said switching in accordance with the detection result of the output voltage detecting means In a chopper type DC / DC converter provided with a control means for controlling switching of an element and controlling an output voltage to a predetermined voltage, a connection line connecting the diode and the output terminal and the output voltage detecting means. Placed between
A switch for voltage detection control is turned off by inputting a stop signal of the DC / DC converter from the outside and disconnects the output voltage detection means from the connection line.
The provided Ji, is characterized in that it has to be disconnected the output voltage sensing means the DC / DC converter stop signal is inputted to supply current from the power source to the output terminal.

Also in order to achieve the above object, the present invention according to claim 2 provides an inductor for connecting one terminal to one terminal of a power source, a diode connected to the other terminal of the inductor, and One electrode is connected to a connection point between the inductor and the diode, the other electrode is connected to a switching element connected to the other terminal of the power supply, and a connection line connecting the diode and the first output terminal, an output voltage detecting means for detecting the voltage boosted by said inductor, in accordance with the detection result of the output voltage detecting means performs switching control of the switching element, and control means for controlling the output voltage to a predetermined voltage In a chopper type DC / DC converter, a CMOS inserted in a connection line connecting the diode and the first output terminal Type regulation circuit, and is connected between the regulation circuit and the first output terminal, and is turned off by receiving a stop signal of the DC / DC converter from the outside, and the regulation circuit is turned off. Switching means for disconnecting the conduction state between the rate circuit and the first output terminal; and a second output terminal for sending the output of the regulation circuit to the second electronic circuit having the low current consumption mode as an output voltage. In addition to being provided, the output of the regulation circuit via the switching means is sent as an output voltage from the first output terminal to the first electronic circuit.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on the illustrated embodiments.

FIG. 1 shows DC / D in one embodiment of the present invention.
It is a circuit diagram showing a C converter, and the description of the parts described in the conventional example will be omitted.

In FIG. 1, CKT1 is a converter. C1 is a capacitor , L1 is an inductor (electrical induction element), Q1 is a switching transistor, SBD1 is a Schottky diode, IC3 is the same DC / DC converter control IC as IC5 in FIG. 2, C2 is a smoothing capacitor, and R1 and R2 are Output voltage monitoring resistor, Q3 is a switch for disconnecting the load of the resistors R1 and R2, IC4 is the same CMOS regulation IC as IC6 of FIG. 2, S
BD2 is a Schottky diode, Q4 is a transistor for turning on / off the output V _OUT2 , and Q2 is a transistor for turning on / off DC / DC.

The battery voltage V _BAT is supplied via the input terminal V _in to the power supply V _CC of the control IC 3, the inductor L1 and the capacitor C.
1 is being supplied.

The inductor L1, the switching transistor Q1, the Schottky diode SBD1, and the smoothing capacitor C2 are a basic set of a chopper type step-up DC / DC converter.

In recent years, CMs including resistors R1 and R2 built-in
DC / DCIC of OS is sold by each electric maker, but if R1 and R2 also have high resistance, the leak is large. Therefore, the resistance is slow and the input is slow because it is also composed of CMOS. There are many problems that fluctuations are likely to appear in the output, and output stability is weak even with fluctuations in the output load.

Therefore, in this embodiment, as the IC3, a bipolar control IC such as the above-mentioned "MB3776A manufactured by Fujitsu Limited" is used. Further, by setting the resistances R1 and R2 to about several KΩ, the output can be stabilized.

Chopper type DC using inductance
/ DC is different from the transformer type, the input side and output side of DC / DC are not separated in terms of DC, that is, the control I
C3 is also turned off, the input V _in would be output through the inductor L1. That is, the converter CKT1 is said to be for boosting for the above reason.

The output of CKT1 is set by R1 and R2.
At 5.4V, compatibility is good when IC4 is 5V. Normally, between the input and output of CMOS regulation IC4, 0.
A potential difference of 2 V or more is desirable. The output V _OUT1 is sent from the COMS regulating IC 4 through the Schottky diode SBD2, and the output V _OUT2 is sent through the transistor Q4.

When the control terminal CTRL is Hi, the transistor Q2 is turned on, so that the DC / DC capacitor control IC3 operates and both the transistors Q3 and Q4 are turned on. On the other hand, when the control terminal CTRL is L ₀ , since the transistor Q2 is turned off, the DC / DC capacitor control IC3 is stopped and the transistor Q3 and the transistor Q4 are turned off.
Turn off together. Therefore, at this time, the current from the battery voltage V _BAT is the inductor L1 and the Schottky diode SB.
It is supplied to the regulating IC4 through D1, and the output which has become 5V in the regulating IC4 is supplied only to V _OUT1 through the Schottky diode SBD2. Here, there is no actual harm even if the Schottky diode SBD2 is not provided.

At this time, since the transistor Q3 is off, the loads on the resistors R1 and R2 are disconnected, and because the transistor transistor Q4 is also off, the load on the output terminal V _OUT2 side is also disconnected, and the microcomputer IC1 on the output terminal V _OUT1 side is disconnected. Is in the low current consumption mode, the consumption of the battery voltage V _BAT can be made extremely small.

When the DC / DC converter 1 is turned on, C
Since the output of the MOS-regulated for IC4 is branched to V _OUT1 and V _OUT2, the potential difference between the output V _OUT1 and V _OUT2 Trang
This is the difference between the saturation of the transistor Q4 and the forward voltage drop of the Schottky diode SBD2.
Since this is smaller than the forward voltage drop of the protection diode between the power source and each input / output terminal of the microcomputer IC1 and the analog processing IC2, there is no harm in the system. This holds even without the Schottky diode SBD2.

Generally, when these components are mounted, obstacles to automatic surface mounting are capacitors, inductors and transformers. That is, the capacitor C1, the inductor L1, and the capacitor C2 in FIG. 1, the capacitor C3, the transformer T1, and the capacitor C4 in FIG.

Here, the capacitors C1 and C2 have the same scale as the capacitors C3 and C4, but the inductor L1
Comparing the transformer T1 with the transformer T1, the inductor L1 is more advantageous in terms of electrical efficiency, number of terminals required for mounting, size, and cost.

According to the above embodiment, cost, size,
A chopper type DC / DC converter that uses an inductor that is advantageous in performance and the like instead of a transformer is adopted, and when the DC / DC converter is off, the feedback resistors (output voltage detection resistors R1 and R2) are disconnected from the output, In addition, C is provided on the output side of the DC / DC converter.
An output terminal V to which a MOS-type regulating IC IC4 is connected and which directly outputs the output through the IC4 at this time
_OUT1 and an output terminal V _OUT2 for outputting via a transistor Q4 which is turned on / off in conjunction with the DC / DC converter are provided, and when the DC / DC converter is turned off, the transistor Q4 is turned off to reduce the battery voltage V _BAT . It is possible to reduce the standby current consumption as much as possible.

(Correspondence between Invention and Example) In this example, the inductor L1 corresponds to the inductor of the present invention,
The Schottky diode SBD1 corresponds to the diode of the present invention, the switching transistor Q1 corresponds to the switching element of the present invention, the resistors R1 and R2 correspond to the output voltage detecting means of the present invention, and the DC / DC converter controlling IC3. Corresponds to the control means of the present invention. Output terminal V
_OUT1 corresponds to the output terminal of the present invention according to claim 1 , and the transistor Q3 is for voltage detection control of the present invention according to claim 1 .
A transistor Q4 corresponds to a switch , and the transistor Q4 corresponds to the switching means of the present invention.
C4 corresponds to the regulation circuit of the present invention according to claim 2.

The above is the correspondence relationship between each configuration of the embodiments and each configuration of the present invention, but the present invention is not limited to the configurations of these embodiments, and the functions or embodiments shown in the claims or the embodiments It goes without saying that any structure may be used as long as it can achieve the function of.

(Modification) The present invention has been described as applied to a camera such as a single-lens reflex camera, a lens shutter camera, a video camera, etc. However, other optical devices and other devices,
Furthermore, it can be applied as a constituent unit.

Furthermore, the present invention may be constructed by appropriately combining the above embodiments or their techniques.

[0047]

As described above, according to the present invention , cost, size, performance, etc. can be used instead of the transformer.
Connected electronics while making use of an effective inductor
The consumption of the power supply voltage during the standby state of the circuit is extremely
Can be small .

[0048]

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a DC / DC converter according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a conventional DC / DC converter.

[Explanation of symbols]

1 DC / DC converter C1, C2 capacitors L1 inductor Q1-Q4 transistors R1, R2 resistance CKT1 converter SBD1, SBD2 Schottky diode IC4 CMOS type regulation IC

Claims (2)

(57) [Claims] 1. An inductor connecting one terminal to one terminal of a power supply, a diode connected to the other terminal of the inductor, and one electrode connected to a connection point between the inductor and the diode, and the other a switching element is of the electrodes is connected to the other terminal of said power supply, said in
An output terminal that constantly outputs the voltage of the other terminal of the ducter,
Min to a connection line connecting the said output terminal and the diode
Is Toki connected, the output voltage detecting means for detecting the boosted voltage by the inductor, performs switching control of the switching element in accordance with the detection result of the output voltage sensing means, control for controlling the output voltage to a predetermined voltage In a chopper type DC / DC converter including means, the DC / DC converter is arranged between a connection line connecting the diode and the output terminal and the output voltage detection means, and the DC / DC converter is externally provided.
A voltage detection control switch is provided, which is turned off by inputting a stop signal of the DC converter and disconnects the output voltage detection means from the connection line.
DC / DC, wherein a current from the power supply is supplied to the output terminal even when the stop signal of the / DC converter is input and the output voltage detecting means is disconnected.
converter. 2. An inductor connecting one terminal to one terminal of a power supply, a diode connected to the other terminal of the inductor, and one electrode connected to a connection point between the inductor and the diode, and the other. An output voltage detection means connected to a switching element whose electrode is connected to the other terminal of the power supply, and a connection line connecting the diode and the first output terminal, and which detects a voltage boosted by the inductor, Performing switching control of the switching element according to the detection result of the output voltage detection means,
In a chopper type DC / DC converter including a control means for controlling an output voltage to a predetermined voltage, a CMOS type regulation circuit inserted in a connection line connecting the diode and the first output terminal, Connected between the regulation circuit and the first output terminal, and is turned off by receiving a stop signal of the DC / DC converter from the outside, thereby changing the state to the regulation circuit and the first output terminal. And a second output terminal for sending the output of the regulation circuit as an output voltage to the second electronic circuit having the low current consumption mode, and the switching means. DC / characterized in that the output of the regulation circuit via the first output terminal is sent from the first output terminal to the first electronic circuit as an output voltage. C converter.