JP2004129340A - Power supply and electronic component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce power consumption as the entire device, especially that under no load, with a power supply along with an electronic component, in which an output voltage is kept constant by controlling oscillation waveform according to a load. <P>SOLUTION: There are provided a transformer (13), a detecting means (16) which detects an output voltage outputted from a secondary coil (L12) side of the transformer (13) and generates a detection signal, transmission means (17 and 101) which transmit the detection signal generated by the detecting means (16) to a primary coil side of the transformer (13), and control means (14 and Q1) that control a voltage applied to the primary coil (L11) side of the transformer (13) based on the output signal of the transmission means (17). The transmission coefficient of detection signal is so set in the transmission means (17 and 101) that the output signal is kept within a signal range required for the control means (14 and Q1) and that the signal range of the detection signal is requisite minimum. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power supply device and an electronic component, and more particularly, to a power supply device and an electronic component that maintain an output voltage constant by controlling an oscillation waveform according to a load.
[0002]
[Prior art]
FIG. 3 shows a circuit configuration diagram of an example of a conventional power supply device.
[0003]
The conventional power supply device 1 constitutes a switching regulator of a ring choke converter (RCC) system.
[0004]
The configuration includes a bridge diode circuit 11, a smoothing circuit 12, a transformer 13, a control circuit 14, a rectifying and smoothing circuit 15, a detection circuit section 16, a photocoupler 17, and a switching transistor Q1.
[0005]
The input AC voltage / current is supplied to the bridge diode circuit 11 via the resistor R1. The bridge diode circuit 11 rectifies an input AC voltage / current. The voltage / current rectified by the bridge diode circuit 11 is supplied to the smoothing circuit 12. The smoothing circuit 12 includes a choke coil L1 and smoothing capacitors C1 and C2, and smoothes the voltage / current rectified by the bridge diode circuit 11.
[0006]
The smoothed voltage / current is supplied to the transformer 13 via the resistor R1 and to the control circuit 14 via the resistor R2. The transformer 13 includes a primary coil L11, a secondary coil L12, and an auxiliary coil L13.
[0007]
A voltage corresponding to the switching of the switching transistor Q1 is applied to the primary coil L11. A voltage corresponding to the current flowing through the primary coil L11 is generated in the secondary coil L12. The secondary coil L12 is connected to the rectifying and smoothing circuit 15. The rectifying and smoothing circuit 15 includes diodes D11 and D12, capacitors C11 and C12, and a choke coil L2. The rectifying and smoothing circuit rectifies and smoothes the AC current generated in the secondary coil L12, and supplies the rectified and smoothed current to the output terminal Tout.
[0008]
The control circuit 14 includes resistors R2 to R5, capacitors C3 to C5, a diode D1, and a transistor Q2, and forms a so-called self-excited intermittent oscillation circuit, and switches the switching transistor Q1. An auxiliary coil L13 is connected to the control circuit 14, and self-excited oscillation is performed by a current from the auxiliary coil L13. Further, the control circuit 14 is supplied with a control current Ic output from the photocoupler 17. The control circuit 14 performs intermittent oscillation according to the control current Ic from the photocoupler 17. When the control current Ic increases, the off period of the switching transistor Q1 increases, and when the control current Ic decreases, the on period of the switching transistor Q1 shortens.
[0009]
Further, the control circuit 14 rectifies and smoothes the current from the auxiliary coil L13 by the diode D1 and the capacitor C5, and supplies the current to the photocoupler 17. The photocoupler 17 includes a photodiode Dp and a phototransistor Qp, and the emitter current of the phototransistor Qp is controlled according to the amount of light emitted from the photodiode Dp. The current rectified and smoothed by the diode D1 and the capacitor C5 of the control circuit 14 is supplied to the collector of the phototransistor Qp. When the light emission amount of the photodiode Dp increases, the emitter current of the phototransistor Qp increases, and when the light emission amount of the photodiode Dp decreases, the emitter current of the phototransistor Qp decreases. The emitter current of the phototransistor Qp is supplied to the control circuit 14 as a control current Ic to the control circuit 14.
[0010]
The detection current If is supplied from the detection circuit 16 to the photodiode Dp. When the detection current If from the detection circuit 16 is large, the light emission amount of the photodiode Dp is large, and when the detection current If from the detection circuit 16 is small, the light emission amount is small.
[0011]
The detection circuit 16 includes resistors R11 to R15, capacitors C21 and C22, and a control IC 21, detects the output voltage Vout and the output current Iout, and detects the detection current If supplied to the photodiode Dp so that the output voltage Vout becomes constant. Control. The detection circuit 16 controls the detection current If so that the detection current If is small when the output current Iout is small, and the detection current If is large when the output current Iout is large.
[0012]
Here, assuming that the transfer coefficient of the photocoupler 17 is CTR, the current flowing through the photodiode Dp is If, and the control current to the control circuit 14, that is, the collector current of the phototransistor Qp is Ic.
Ic = If × CTR (1)
Is represented by
[0013]
Therefore, the detection current If flowing through the photodiode Dp is given by If = Ic / CTR from Expression (1) (2)
Is represented by
[0014]
[Problems to be solved by the invention]
However, in a conventional power supply device such as an AC adapter, it is desired to reduce the current consumption of the entire device, particularly the current consumption when there is no load. However, in the AC adapter shown in FIG. 3, when there is no load, the starting resistance, the winding load of the transformer 13, the loss of the switching transistor Q10, the loss of the transformer efficiency, the loss of the photodiode of the photocoupler 17, the loss of the detection circuit 16, and the like. appear.
[0015]
The photocoupler 17 has poor transmission efficiency and a low transmission rate CTR. Therefore, in order to obtain the predetermined control current Ic, it is necessary to increase the detection current If. By increasing the detection current If, the current consumption on the secondary coil L12 side of the transformer 13 increases. In particular, since the conversion efficiency of the transformer 13 is applied on the secondary coil L12 side of the transformer 13, the current consumption is larger than the current consumption on the primary coil L11 side of the transformer 13.
[0016]
The present invention has been made in view of the above points, and an object of the present invention is to provide a power supply device and an electronic component that can reduce power consumption of the entire device, particularly, current consumption when there is no load.
[0017]
[Means for Solving the Problems]
According to the present invention, a transformer (13), detecting means (16) for detecting an output voltage output from a secondary coil (L12) side of the transformer (13) and generating a detection signal, and detecting means (16). Transmission means (17, 101) for transmitting the generated detection signal to the primary coil side of the transformer (13), and a primary coil (L11) side of the transformer (13) based on an output signal of the transmission means (17). Control means (14, Q1) for controlling the applied voltage to be applied to the control means (17, 101), and the transmission means (17, 101) maintains the output signal in a signal range required by the control means (14, Q1); The transmission coefficient of the detection signal is set so that the signal range of the detection signal is a necessary minimum.
[0018]
Further, according to the present invention, the transmission means (17, 101) includes a photodiode (Dp) that emits light in response to a detection signal, and a phototransistor (Qp) that outputs a current corresponding to light from the photodiode (Dp). And a transistor (Q10) which forms a Darlington connection with the phototransistor (Qp) constituting the photocoupler (17) and supplies a current to the control means (14, Q1). The transfer coefficient is characterized by being adjusted by the current amplification factor of the Darlington connection.
[0019]
Further, the invention is characterized in that a resistor (R10) is connected between the base and the emitter of the transistor (Q10).
[0020]
Further, the present invention is characterized in that the photocoupler (17) and the transistor (Q10) are integrated and constitute a single component.
[0021]
According to the present invention, the output signal output from the secondary coil (L12) side of the transformer (13) is detected, and the detection signal generated by the detection means (16) for generating the detection signal is transmitted to the transmission means (17, 101), the applied voltage applied to the primary coil (L11) side of the transformer (13) is transmitted to the control means (14, Q1) for controlling the output voltage. 14, Q1) is maintained in the required signal range, and the transmission coefficient of the detection signal is set so that the signal range of the detection signal is the minimum necessary. Since the current consumption at the time of load can be reduced, the power consumption of the entire device can be reduced, and particularly, the current consumption at the time of no load can be significantly reduced.
[0022]
The reference numerals are merely examples, and the present invention is not limited to these.
[0023]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 is a circuit diagram showing an embodiment of a power supply device according to the present invention. 3, the same components as those of FIG. 3 are denoted by the same reference numerals, and the description thereof will be omitted.
[0024]
The power supply device 100 of the present embodiment has a configuration in which a current amplification circuit 101 is provided between a photocoupler and an intermittent oscillation circuit.
[0025]
The current amplifying circuit 101 includes a transistor Q10 and a resistor R10, and together with the phototransistor Qp constituting the photocoupler 17, constitutes an Darlington-connected amplifying circuit.
[0026]
Transistor Q10 is formed of an NPN transistor. The voltage generated by the rectifying and smoothing circuit including the diode D1 and the capacitor C5 is applied to the collector of the transistor Q10. The resistor R10 is connected between the base and the emitter of the transistor Q10. The linearity of the current amplifying circuit 101 in a small current region is improved by the resistor R10.
[0027]
The emitter current of the phototransistor Qp is amplified according to the current amplification factor hfe. The collector is supplied with a drive power supply voltage from a rectifying and smoothing circuit, and the emitter is connected to the base of the transistor Q1 via a resistor.
[0028]
Here, assuming that the emitter current of the transistor Q10 is Ic and the current amplification factor of the transistor Q10 is hfe,
The current amplification rate obtained by combining the photocoupler 17 and the transistor Q10 is
(CRT x hfe)
Can be represented by
[0029]
Therefore, the emitter current Ic of the transistor Q10 is
Ic = If × (CTR × hfe) (3)
Can be represented by Therefore, the current If flowing through the photodiode Dp is
If = Ic / (CTR × hfe) (4)
Can be represented by
[0030]
Comparing Expression (4) with the output current Ic of the conventional photocoupler 17 shown in Expression (2), the current If can be reduced in proportion to the current amplification factor hfe of the transistor Q10. By reducing the current If, the current consumption on the secondary coil L12 side of the transformer 17 can be significantly reduced.
[0031]
For example, when the input AC voltage is 100 V, the power consumption can be reduced by 10 mW.
[0032]
FIG. 2 shows a characteristic diagram of the control current Ic with respect to the detection current If. In FIG. 2, the broken line indicates the conventional characteristic, and the solid line indicates the characteristic of the present embodiment.
[0033]
When the current amplification factor becomes (CTR × hfe) as in the present embodiment, the characteristic of the control current Ic with respect to the detection current If as shown by the solid line in FIG. The amplification factor shifts in the direction of arrow A as compared with the case where only the CTR is used.
[0034]
As the characteristic of the control current Ic with respect to the detection current If shifts in the direction of arrow A, the detection current range ΔIf for obtaining the predetermined control current range ΔIc shifts in the direction of arrow X, that is, in the direction in which the current value decreases. Therefore, current consumption on the secondary coil L12 side can be reduced.
[0035]
Note that the current amplification circuit 111 may be integrated with the photocoupler 17 and provided as one component.
[0036]
Further, in the present embodiment, the current amplifying circuit is provided between the photocoupler 17 and the control circuit 14, but the current consumption can be reduced by improving the conversion efficiency of the photocoupler 17.
[0037]
In the present embodiment, a so-called AC adapter that converts an AC voltage to a DC voltage as a power supply device has been described as an example. However, the present invention is not limited to this, and at least a transformer and a transformer Detecting means for detecting an output voltage outputted from the secondary coil side of the transformer and generating a detection signal; transmitting means for transmitting the detection signal generated by the detecting means to the primary coil side of the transformer; The present invention can be applied to a power supply device having control means for controlling an applied voltage applied to a primary coil side of a transformer based on a signal.
[0038]
【The invention's effect】
As described above, according to the present invention, the current consumption can be reduced to a minimum by adjusting the transmission coefficient of the transmission means, and in particular, the current consumption when there is no load can be reduced. It has features such as a reduction in current consumption, especially when no load is applied.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of an embodiment of a power supply device of the present invention.
FIG. 2 is a characteristic diagram of a control current Ic with respect to a detection current If.
FIG. 3 is a circuit configuration diagram of an example of a conventional power supply device.
[Explanation of symbols]
Reference Signs List 100 power supply device 11 bridge diode circuit, 12 smoothing circuit, 13 transformer 14 control circuit, 15 rectification smoothing circuit, 16 detection circuit 17 photocoupler L11 primary coil, L12 secondary coil, L3 auxiliary coil Q1 switching transistor, Dp photodiode Qp Phototransistor 101 Current amplifier circuit Q10 Transistor, R10 resistor

Claims (6)

With a transformer,
Detecting means for detecting an output voltage output from a secondary coil side of the transformer and generating a detection signal;
Transmitting means for transmitting the detection signal generated by the detecting means to a primary coil side of the transformer;
Control means for controlling an applied voltage applied to a primary coil side of the transformer based on an output signal of the transmission means,
The transmission means is configured such that the transmission coefficient of the detection signal is set so that the output signal is maintained in a signal range required by the control means, and the signal range of the detection signal is minimized. Power supply device characterized. The transmission means, a photodiode that emits light in response to the detection signal,
A photocoupler having a phototransistor that outputs a current according to light from the photodiode,
A Darlington connection with the phototransistor constituting the photocoupler, and a transistor for supplying current to the control means,
The power supply device according to claim 1, wherein the transfer coefficient is adjusted by a current amplification factor of the Darlington connection. 3. The power supply device according to claim 2, wherein a resistor is connected between the base and the emitter of the transistor. The power supply device according to claim 2, wherein the photocoupler and the transistor are integrated to form a single component. A photodiode that emits light in response to an input signal;
A photocoupler having a phototransistor that outputs a current according to light from the photodiode,
An electronic component, wherein a Darlington connection is formed with the phototransistor forming the photocoupler, and a transistor that outputs an output current is integrated to form a single component. The electronic component according to claim 5, wherein a resistor is connected between the base and the emitter of the transistor.

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