JP2001136736A - Power supply apparatus and electrical apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a power supply apparatus small-sized and at a low cost and an electrical apparatus using it by a method, where a circuit structure which enables the reduction of the power loss of the power supply apparatus is employed. SOLUTION: A power supply apparatus comprises a switching device 3, which switches a power supply voltage supplied from an input power supply circuit 2 at prescribed timings, an inductance element 4 which generates a counter electromotive force when the power supply voltage is cut off by the switching device 3, an output capacitor 5 which is charged by the counter electromotive force generated by the inductance element 4 to lower the impedance of the output, a monitor circuit 6 which detects an output current, and when an abnormal voltage is inputted, stops the operation of the switching device 3, a drive circuit 7 which controls and drives the operation of the switching device 3 according to a signal from the monitor circuit 6, a diode 8 of which a path, through which a current produced by the generated counter electromotive force flows is composed and a characteristic improvement circuit 9, which makes the characteristic curve of the output current with regard to the output-voltage, a hanging-type.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device called a DC-DC converter used for electric equipment such as a multifunctional telephone, a vacuum cleaner and a charging device for a secondary battery such as a lithium ion battery. It relates to a circuit configuration.

[0002]

2. Description of the Related Art Conventionally, in an electric device using a semiconductor device such as a one-chip microcomputer, a stable output voltage characteristic is required as a power supply of the semiconductor device, and a high efficiency is required due to external restrictions of each device. There is a need for a small power supply. To satisfy this demand, FIG.
A power supply device of a type called a DC-DC converter as shown in FIG.

A power supply device 1b shown in FIG. 5 comprises an input power supply circuit 2 comprising a DC power supply 2a and an input capacitor 2b, a switching element 3 comprising a transistor 11, an inductance element 4, an output capacitor 5, resistors 21, 22 and 24, a Zener diode 23, a monitoring circuit 6 including transistors 19 and 20, a transistor 14, a resistor 1
The drive circuit 7 includes 2 to 14 and a diode (hereinafter referred to as “flywheel diode”) 22.

An input power supply circuit 2 is connected to a transistor 1 via a terminal T1 (hereinafter, referred to as a "voltage input terminal T1").
1, the collector side of the transistor 11 (the wiring L 'in FIG. 5) is connected to the terminal T3 (hereinafter referred to as "output terminal T3") via the inductance element 4,
The output capacitor 5 is connected between the output terminal T3 and the terminal T2 (hereinafter, referred to as “reference voltage terminal T2”).
The collector output of the transistor 19 of the monitoring circuit 6 is connected to the base of the transistor 14 of the driving circuit 7 and to the wiring L ′ via the capacitor 16. Further, the reference voltage terminal T2 is also connected to the wiring L 'via the diode 8.

The operation will be described. First, the power supply 1
When a load such as a motor or a semiconductor device is connected between the output terminal T3 and the reference voltage terminal T2 and the DC power supply 2a is set to a predetermined voltage V1, the voltage is applied to the subsequent circuits via the voltage input terminal T1. Apply and become operational. When this voltage is applied, when the transistor 14 is turned on, the transistor 1
1 is conducted, and a current (hereinafter, referred to as “output current”) flows through the monitoring circuit 6 and the load via the inductance 4. At this time, since a base current flows through the transistor 14 even through the capacitor 16, the transistor 14
, The collector current increases, and the transistor 11 rapidly saturates.

When the output current is large, the output current flows to the monitoring circuit 6, and a voltage for conducting the transistor 20 is generated in the resistor 22, and when the transistor 20 is turned on, the transistor 19 is turned on. On the other hand, when the output current is small and the output voltage rises, the voltage generated at the resistor 24 causes the transistor 19 to conduct. Thus, the transistor 19
Is turned on, the base voltage of the transistor 14 becomes low, so that the transistor 14 is turned off and the transistor 11 is turned off. At this time, since a back electromotive force is generated in the inductance 4, a current due to the back electromotive force continues to flow in the load and the diode 8.

Thereafter, when the back electromotive force gradually decreases and the output current decreases, the voltage drop due to the resistor 22 decreases and the transistor 20 is cut off. When the transistor 19 is cut off, the base voltage of the transistor 14 is turned off. Rises, so that the transistor 11 becomes conductive again. The output current is charged into the output capacitor 5 while repeating the above operation cycle, so that a substantially constant output current can be supplied to the load.

[0008]

However, the characteristics of the output voltage and the input current at the terminal T1 with respect to the output current flowing through the load of the conventional power supply device 1b are as shown in the waveform diagram of FIG. After exceeding the values (points B and B 'in FIG. 5), the output voltage and the input current both have characteristics of gradually decreasing, and the cycle of the above-described operation cycle becomes shorter as the output current increases. It works to be. Therefore, there is a problem that power loss due to elements such as the transistor 11 and the inductance element 4 increases, and each element and the power supply generate heat. In addition, when the heat generated by each element increases, it is necessary to perform a heat radiation process on the package and the substrate using the same, so that the outer shape of each element increases, and the outer shape of the entire power supply device and the device using the same also increase. There are also problems.

Therefore, the present invention solves these problems and makes it possible to easily form a small and inexpensive power supply device and an electric apparatus using the same by adopting a circuit configuration that reduces the power loss of the power supply device. The purpose is to.

[0010]

According to a first aspect of the present invention, there is provided a power supply device comprising: a switching element and an inductance element connected in series between a voltage input terminal and an output terminal; A monitoring circuit for detecting a current flowing to the output terminal and preventing a current of a certain value or more from flowing and a voltage of the output terminal from rising beyond a predetermined value, and a current detection result in the monitoring circuit. A drive circuit for turning off the switching element when the voltage of the output terminal is higher than the predetermined value, in addition to when the switching element is turned off, and a back electromotive force of the inductance element when the switching element is turned off. A flywheel diode for forming a path through which current flows,
The switching element is turned off via the drive circuit until the current due to the back electromotive force of the inductance element is a current having a value smaller than the fixed value and is equal to or less than a current defining a forward voltage of the flywheel diode. And a characteristic improving circuit for conducting the switching element through the driving circuit thereafter. In the power supply device according to the present invention, a switching element and an inductance element connected in series between the voltage input terminal and the output terminal, and a current flowing to the output terminal, and a current equal to or more than a certain value flows. A driving circuit for turning off the switching element when a current detection result of the monitoring circuit is larger than the predetermined value, and a driving circuit for turning off the inductance element when the switching element is turned off. A flywheel diode for forming a path through which a current flows due to an electromotive force, and one end connected to a connection point between the flywheel diode (8) and the inductance element and another connection point between the monitoring circuit and the drive circuit. It has a diode (17) connected at the end, so that the current due to the back electromotive force of the inductance element is reduced. And having a characteristic correction circuit to the forward voltage is eliminated thereby turning on the switching element and thereafter the switching element to cut-off state of the diode (17) Te. further,
A power supply according to a third aspect is the power supply according to the second aspect, wherein a resistor (18) is connected in series to the diode (17) of the characteristic improvement circuit. The power supply device according to claim 4 is:
4. The power supply device according to claim 2, wherein the monitoring circuit prevents a current of the predetermined value or more from flowing to the output terminal, and furthermore, a voltage of the output terminal exceeds a predetermined value. 5. It is also for preventing the rise, the drive circuit, when the current detection result in the monitoring circuit is greater than the predetermined value, in addition to when the voltage of the output terminal is greater than the predetermined value The switching element is turned off. With such a configuration, it is possible to reduce the internal loss of the circuit and simplify the heat radiation processing while having a simple circuit configuration, and to realize a small and inexpensive electronic component or a small-sized integrated part of these components. A power supply device can be formed by using the semiconductor device of (1).

The electric device according to claim 5 is an input power supply circuit for performing rectification and smoothing of a commercial power supply, and the output thereof is received by the voltage input terminal. A power supply device, an output capacitor for smoothing an output voltage connected to the output terminal thereof, and a semiconductor device connected to a power supply voltage terminal for receiving operating power. . With such a configuration, a small and inexpensive power supply device can be easily used in a power supply circuit of a semiconductor application product.

[0012]

FIG. 1 is a block diagram showing an embodiment of the present invention.
This will be described in detail with reference to FIGS. In this specification, the same or similar circuit elements are denoted by the same reference symbols throughout the drawings, and redundant description is omitted. FIG. 1 is a circuit diagram of a power supply device called a DC-DC converter using the present invention. The configuration is such that a power supply voltage is turned on or off at a predetermined timing (hereinafter referred to as "switching").
Switching element 3 for switching and switching element 3
Element 4 for generating a back electromotive force when the power supply voltage is cut off by the power supply, and an electrolytic type output capacitor 5 for charging by the back electromotive force generated by the inductance element 4 and lowering the output impedance.
A monitoring circuit 6 for detecting an output current and stopping the operation of the switching element 3 when an abnormal voltage is input, and a drive for controlling and driving the switching element 3 according to a signal from the monitoring circuit 6 A circuit 7, a diode 8 (hereinafter, referred to as a “flywheel diode”) forming a path through which a current flows due to the generated back electromotive force, and an output voltage sharply increases when the output voltage characteristic with respect to the output current exceeds a predetermined current value. And a characteristic improving circuit 9 for reducing the drooping characteristics.

The configuration of each circuit will be described in more detail. The switching element 3 includes a PNP transistor 15 having an emitter connected to a terminal T1 (hereinafter, referred to as a "voltage input terminal T1") and a collector connected to an inductance element 4. The inductance element 4 is made of ferrite, amorphous, or the like. And a coil wound around the core. Further, the monitoring circuit 6 includes a resistor 22 for detecting a current flowing through the load (hereinafter, referred to as “output current”), a terminal T3 (hereinafter, referred to as “output terminal T3”), and a terminal T2 (hereinafter, referred to as “reference voltage terminal T2”). ), A zener diode 23 and a resistor 24 connected in series.
And a base connected to the output terminal T3 and a resistor 2
2 and the inductance element 4, the emitter is connected, and the collector is connected via the resistor 21 to the Zener diode 23.
The PNP-type transistor 20 connected to the connection point of the anode and the resistor 24 and the base is connected to the anode side of the Zener diode 23 and the emitter is connected to the reference voltage terminal T2 to control the drive circuit 7 by the collector output. And an NPN-type transistor 19. In the drive circuit 7, the collector is connected to the base of the transistor 11 via the resistor 13, the emitter is connected to the reference voltage terminal T2 via the resistor 15, and the base is connected to the voltage input terminal T1 via the resistor 12. And an NPN transistor 14. The characteristic improvement circuit 9 has a flywheel diode 8 as a cathode.
And the anode is connected to the resistor 18
, And a diode 17 connected to the collector of the transistor 19 through the gate.

The connection between the circuit configurations will be further described. The power supply voltage is connected to the emitter of the transistor 11 via the voltage input terminal T1, the collector side (the wiring L in FIG. 1) of the transistor 11 is connected to the output terminal T3 via the inductance element 4, and the output terminal T3 is connected to the reference terminal. An output capacitor 5 is connected between the output capacitor 5 and the voltage terminal T2.
The collector output of the transistor 19 of the monitoring circuit 6 is connected to the base of the transistor 14 of the driving circuit 7 and to the wiring L via the characteristic improving circuit 9. Further, the reference voltage terminal T2 is also connected to the wiring L via the diode 8.

Next, the circuit operation of the present invention will be described.
First, the output terminal T3 of the power supply device 1a and the reference voltage terminal T2
And a device serving as a load such as a motor or a semiconductor device. A DC power supply 2a is connected to a voltage input terminal T1 and an electrolytic capacitor 2b provided in parallel with the DC power supply 2a to reduce the impedance. Input power supply circuit 2 is connected. Then, the DC power supply 2a is set to a predetermined voltage V
When it is set to 1, a voltage is applied to the subsequent circuits via the voltage input terminal T1, and operation becomes possible. When the transistor 14 is turned on by this voltage application, the transistor 11 is turned on.
Is conducted, and the monitoring circuit 6
Also, the output current flows to the load. At this time, since the diode 17 acts as a capacitor on the base of the transistor 14 to apply a positive feedback via the resistor 18, the transistor 11 is quickly saturated and conducts.

When the output current is large, the output current flows to the monitoring circuit 6, and a voltage for conducting the transistor 20 is generated in the resistor 22, and when the transistor 20 is turned on, the transistor 19 is turned on. On the other hand, in a case where the output voltage is increased when the output current is small and the transistor 20 does not conduct, the current flows through the Zener diode 23 to generate a voltage at the resistor 24 so that the transistor 19 is rendered conductive. Become. Thus, when the transistor 19 is turned on,
Since the base voltage of the transistor 14 becomes low, the transistor 14 is turned off and the transistor 11
Is shut off. At this time, since a back electromotive force is generated in the inductance 4, an output current continues to flow through the load and the diode 8 due to the back electromotive force.

Thereafter, the back electromotive force gradually decreases, and the current due to the back electromotive force decreases to shut off the transistor 20, or the output voltage drops below a predetermined value, so that no current flows through the Zener diode 23 and the resistance is reduced. When the voltage at 24 drops, transistor 19 is turned off. At this time, the voltage of the wiring L is lower than the reference voltage (0 (V)) by the forward voltage (VF (V)) of the diode 8 as shown in FIG. Therefore, the base voltage (VB14) of the transistor 14 is set to the voltage shown by the equation (1) via the diode 17 and the resistor 18 of the characteristic improving circuit 9. Actually, since the resistance value (R12) of the resistor 12 is sufficiently larger than the resistance value (R18) of the resistor 18, the base voltage is substantially the reference voltage. Therefore, the base voltage of the transistor 14 becomes a value smaller than the voltage between the base and the emitter, the transistor 14 remains cut off, and the output current due to the back electromotive force continues to flow. Note that the resistor 18 may be omitted, but is provided to protect the diode 17 from overcurrent.

[0018]

[Formula 1] When the base voltage of the transistor 14 rises and the transistor 14 conducts again, the back electromotive force and the output current further decrease, and the current flowing through the diode 8 becomes forward voltage (generally 0.4 V).
V to 1.7 V) or less (hereinafter referred to as “forward current”), and after the forward voltage of the diode 17 has disappeared.

The output current is charged to the output capacitor 5 while repeating the above-described operation cycle, and a substantially constant output current and voltage are supplied to the load, as shown in FIG. The specified output current value (A in FIG. 2)
Until the point), a constant output voltage is output, and when the output current value exceeds a specified output current value, a drooping output characteristic is obtained in which the output voltage sharply decreases. At this time, the characteristics of the input current at the terminal T1 are as shown in FIG. By having such electrical characteristics, power loss when the output terminal T3 is short-circuited to the reference potential or when an overload is connected can be greatly reduced, so that the heat generation of the circuit is accordingly reduced. As a result, heat radiation processing becomes easy, and downsizing of circuits and devices becomes possible. For example, the power loss in the circuit of the present invention can be reduced by about 40% as compared with the conventional circuit, and can be reduced to about 1 W.

FIG. 3 shows an example of the voltage of the wiring L and the waveform of the current flowing through the inductance 4 in the power supply device 1a of FIG. Note that the ripple voltage and the like are omitted in FIG. Vsat in FIG.
Indicates the saturation voltage at the time of conduction, and t1 is the switching element 3
3 shows the cycle time of the operation cycle. Further, the current flowing through the inductance element 4 in FIG. 3B is represented by a voltage V1 (V) across the capacitor 2b, a voltage V2 (V) across the capacitor 5 and a voltage across the resistor 22. Is Vbe (V), the inductance value of the inductive element 4 is L (H), the forward voltage of the diode 8 due to the back electromotive force is VF (V), and the elapsed time is Δt (s), the transistor 11 conducts. When the transistor 11 is turned off and charged by the back electromotive force, the charging current is expressed by the following equation (2).

[0021]

[Formula 2]

[0022]

[Equation 3] The output current and the value of each constant may be set to a necessary current according to the connected load. For example, when the peak value of the output current is several hundred mA, the cycle t of the operation cycle is t
1 is several μs to several tens of μs, the inductance value of the inductance element 4 is several mH to several tens mH, the resistance value of the resistor 22 is several Ω to several tens Ω, and the resistance value of the resistance 12 is several M.
The resistance value of the resistor 18 may be set to about several hundred Ω.

FIG. 4 shows an embodiment as an application circuit when the power supply device 1a of FIG. 1 is used in a vacuum cleaner or the like. The application circuit 50 of FIG. 4 includes a plug 51 for inputting an AC voltage (so-called “commercial power”), and a diode element 52 for rectifying and smoothing the AC power to obtain the power supply voltage of the power supply device 1a of the present invention. An input power supply circuit including a power supply voltage from the power supply device 1a, a semiconductor device 53 such as a one-chip microcomputer that operates by being supplied with a power supply voltage, and an interrupter circuit 54 for transmitting a control signal from the semiconductor device 53. A driving device 60 such as a triac that controls conduction and interruption of an AC power supply in accordance with a signal input by the interrupter circuit 54;
And a load 59 such as a motor operated by an AC power supply controlled by the power supply.

The connection relation of each part will be described. The AC power supply has one end connected to the reference voltage terminal T2 of the power supply device 1a and the reference voltage (GND) side of each circuit via the plug 51, and the other end connected to the load 59 and the anode of the diode element 52. . The power supply voltage rectified and smoothed by the diode element 52 and the input capacitor 2c is connected to the voltage input terminal T1 of the power supply device 1a of the present invention, and the output terminal T3 of the power supply device 1a is connected to the power supply voltage terminal (VDD) of the semiconductor device 53. The output S of the semiconductor device 53 is connected to the anode of the light emitting diode 56 of the interrupter circuit 54 via the resistor 55. Light emitting diode 56
Is received by a light receiving element 57 such as a pin diode connected between the anode and the gate of the triac of the driving device 60 via the resistor 58, and the other anode of the triac is connected to the load 59. With such a circuit configuration, it is possible to easily control the load of a motor or the like using a commercial power supply such as 100 V or 220 V.

The present invention is not limited to the above embodiment. For example, a full-wave rectifier circuit using a diode bridge circuit, a transformer with a center tap, or the like may be used as an input power supply circuit. A power supply circuit is provided with a switch circuit for operation control, a display device such as a light emitting diode is provided for displaying an operation state, or a power supply voltage of a one-chip microcomputer or the like is obtained by dividing an output voltage of the power supply device of the present invention with a resistor or the like. It may be used as. Further, the voltage detection circuit of the monitoring circuit may have any circuit configuration as long as the circuit configuration can detect the current flowing to the load. Further, the circuit of the present invention may be formed using only a single electronic component, or may be formed in a semiconductor device in which only a circuit portion including a transistor, a diode, and a resistor is integrated into one. Further, a circuit configuration using MOS transistors may be used instead of the circuit using bipolar transistors in FIG.

[0026]

According to the present invention as described above, claim 1
In the power supply device according to any one of the first to fourth aspects, the internal loss is reduced and the heat radiation process can be simplified while having a simple circuit configuration. Therefore, small and inexpensive electronic components or parts thereof are integrated into one. It is possible to easily form a power supply device using a miniaturized and small semiconductor device, and there is an effect that a small and inexpensive power supply device can be easily formed.

In the electric device according to the fifth aspect, a small and inexpensive power supply device can be easily used in a power supply circuit of a semiconductor application product, so that the outer shape of the product is less restricted and the design is reduced. This has the effect that the period is shortened, the design cost is reduced, and the unit price of the product can be reduced.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating an embodiment of the present invention,

FIG. 2 is a waveform chart showing characteristics of an output voltage and an input current according to the embodiment of the present invention;

FIG. 3 is a waveform chart showing characteristics of main parts according to the embodiment of the present invention;

FIG. 4 is a configuration diagram showing an application device using the circuit of the present invention,

FIG. 5 is a circuit diagram showing a conventional circuit example;

FIG. 6 is a waveform chart showing characteristics of a conventional circuit example.

[Explanation of symbols]

 1a: Power supply device 2: Input power supply circuit 3: Switching element (PNP transistor) 4: Inductance element 5: Output capacitor 6: Monitoring circuit 7: Drive circuit 8: (Flywheel) diode 9: Characteristic improvement circuit

Claims (5)

[Claims] A switching element and an inductance element connected in series between a voltage input terminal and an output terminal, a current flowing through the output terminal being detected, and a current of a predetermined value or more flowing therethrough; A monitoring circuit for preventing the rise from exceeding a predetermined value, and also when the voltage of the output terminal is higher than the predetermined value in addition to when the current detection result in the monitoring circuit is higher than the predetermined value. A drive circuit for interrupting the switching element, a flywheel diode for forming a path through which a current due to the back electromotive force of the inductance element flows when the switching element is interrupted, and a current due to the back electromotive force of the inductance element Is a current having a value smaller than the fixed value and is equal to or less than a current that defines a forward voltage of the flywheel diode. In power supply and a characteristic improvement circuit for conducting said switching element via the driving circuit to and then the switching element is interrupted state via the drive circuit. 2. A switching circuit and an inductance element connected in series between the voltage input terminal and the output terminal, and a monitoring circuit for detecting a current flowing to the output terminal and preventing a current of a predetermined value or more from flowing. And a drive circuit that cuts off the switching element when the current detection result in the monitoring circuit is larger than the fixed value, and a path through which a current flows due to the back electromotive force of the inductance element when the switching element is cut off. A flywheel diode to be formed, and a diode (17) having one end connected to a connection point between the flywheel diode (8) and the inductance element and the other end connected to a connection point between the monitoring circuit and the drive circuit. ), And the current due to the back electromotive force of the inductance element is reduced to reduce the current of the diode (17). Power supply and a characteristic improvement circuit for conducting said switching element and then the switching element to shut off until the direction voltage is removed. 3. The diode (1) of the characteristic improvement circuit.
3. The power supply device according to claim 2, wherein the resistor is connected in series with the resistor. 4. The monitoring circuit according to claim 1, wherein the monitoring circuit prevents a current exceeding the predetermined value from flowing through the output terminal and also prevents a voltage at the output terminal from rising beyond a predetermined value. Wherein the drive circuit cuts off the switching element even when the voltage of the output terminal is higher than the predetermined value, in addition to when the current detection result in the monitoring circuit is higher than the predetermined value. The power supply device according to claim 2 or 3, wherein: 5. An input power supply circuit for performing rectification and smoothing of a commercial power supply, a power supply device according to any one of claims 1 to 5, wherein an output thereof is received by said voltage input terminal, and said output terminal thereof. An electric apparatus comprising: an output capacitor for smoothing an output voltage connected to a power supply terminal; and a semiconductor device connected to a power supply voltage terminal for receiving operating power.