JP2894954B2 - Multi-output power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multiple output power supply,
In particular, it relates to a switching type multiple output power supply device.

[0002]

2. Description of the Related Art A conventional technique of this kind will be described with reference to the drawings.

FIG. 6 is a circuit diagram showing a conventional example, and FIG. 7 is a block diagram showing an application example of the conventional example.

FIG. 6 and FIG. 7 show this conventional example.
JP-A-3-277471: This is the content described in “Multi-output switching power supply device”.

In FIG. 6 and FIG. 7, the current of the primary winding 41a of the switching transformer 1 is
When the FET 42 is turned on and off to perform switching, a voltage is generated in the secondary winding 1b of the switching transformer 41, and the rectifying and smoothing circuit 4 of the diode D1 and the capacitor C1 is formed.
3, the DC output voltage V ₁ (+12 V) is generated.
The output voltage V ₁ is divided by resistors R51 and R52,
The divided voltage output is supplied to the voltage detection amplifier 55.

When the output voltage V ₁ becomes higher than +12 V,
The divided output also increases accordingly, and the voltage detection amplifier 54
The input voltage of the control terminal 54c becomes higher than a predetermined value, the conduction between the main terminals 54a and 54b is conducted, a current flows to the photodiode PCa of the photocoupler PC via the resistor R53, and the phototransistor PCb is turned on. The PWM control circuit 45 composed of an IC (integrated circuit) is a MOS F
It controls the switching operation of the ET 42, and controls the on / off time width ratio (duty) of the switching pulse supplied to the switching transmission circuit and the MOS FET 42.

An output voltage detection amplifier 54 and resistors R55 and R56 detect an output voltage Va of a rectifying / smoothing circuit 46 comprising a diode D2 and a capacitor C2, and when the voltage Va exceeds a predetermined value, the output voltage detection amplifier. 5
4 between the main terminals 54a and 54b and the photocoupler P
The photodiode PCa of C is issued. Control input terminals 55c and 54c of output voltage detection amplifiers 55 and 54 when transistors Tra and Trb are turned on, respectively.
Of each output voltage detection amplifier 55
And 54 are prevented from conducting between the main terminals. The control signal CONT is directly input to the base of the transistor Tra, and the control signal CONT is input to the base of the transistor Trb via the inverter 56.

When the control signal CONT is at a low level, the transistor Tra of the control unit 50 of the power supply device PS is off and the transistor Trb is on. Therefore, the control unit 50 controls the output of the rectifying / smoothing circuit 43, that is, the first output voltage V
₁ is detected and fed back to control the PWM control circuit 45, whereby the MOS FET 42 is feedback-controlled. As a result, the voltages V ₁ is maintained at a predetermined value.

[0009]

The conventional multi-output power supply device stabilizes the output voltage by receiving a control signal that detects a load state and a no-load state from a device to which the conventional multi-output power supply device is applied. Therefore, there is a problem that it is necessary to provide a detection circuit for detecting a load state and a no-load state in an applied device.

[0010]

SUMMARY OF THE INVENTION A multi-output power supply according to the present invention is characterized in that a switching voltage inputted to a primary winding of a transformer is applied to a first secondary winding side of the transformer by means of a first load current value. A first output voltage generating means for generating a preset first direct-current voltage having a first smoothing circuit including a first element which varies, and a leakage inductance approximating a preset numerical value. A second smoothing circuit including a second element whose impedance varies according to a second load current value on a second secondary winding side of the transformer, and a three-terminal regulator connected to the second smoothing circuit. Second output voltage generating means for generating a second DC voltage set in advance, and detection voltages of first and second output voltages of the first smoothing circuit and the second smoothing circuit, respectively. Switching voltage control means for controlling a pulse width and a cycle of the switching voltage in accordance with a comparison result of each of the output voltage generation means and the second output voltage generation means with a preset reference voltage, The first DC voltage and the second DC voltage are stabilized even when the respective loads of the first output voltage generating means and the second output voltage generating means fluctuate.

[0011] multiple-output power supply unit of the present invention have a second secondary winding comprising a leakage inductance of numbers that approximate the preset numerical value as the primary winding and the first secondary winding <br A transformer, an input circuit connected to both terminals of the primary winding and including a switching transistor, and a first rectification smoothing connected to both terminals of the first secondary winding to rectify and smooth the input voltage. A circuit, a first dummy resistor connected to an output side of the first rectifying / smoothing circuit, and a difference between an output voltage of the first rectifying / smoothing circuit and a preset first reference voltage. a first comparator circuit which, with the second rectifier connected to the input voltage to both terminals of the secondary winding, and smoothing, the second rectifying smoothing circuit for constant output voltage on the basis of the leakage inductance, the Three-terminal regis connected to the output side of the second rectifying and smoothing circuit , A first capacitor and a second dummy resistor connected in parallel to the output side of the three-terminal regulator, and a second reference voltage that has been established in advance by detecting the output voltage of the second rectifying and smoothing circuit. Output the difference of
A comparison circuit, a frequency modulation circuit that outputs a signal frequency-modulated with respect to a preset center frequency corresponding to the output voltage from the second comparison circuit, and the signal output from the frequency modulation circuit And a pulse width modulation control circuit for switching-controlling the transistor based on the output voltage from the first comparison circuit ,
Smooth circuit has variable inductance due to passing current loss
A second rectifying / smoothing circuit including a first choke coil;
Is a second variable whose inductance varies with the passing current value.
It is characterized by including a choke coil .

[0012]

Next, the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

In FIG. 1, the present embodiment has a transformer (hereinafter referred to as T) 100, an input circuit 110 connected to both terminals of a primary winding (hereinafter referred to as l ₁ ) 3 of T100, and a secondary winding (hereinafter referred to as l) of T100. ₂ ) Rectifying smoothing circuit 200 connected to both terminals of 4
A dummy resistor (hereinafter referred to as Rp) 31 connected between output terminals of the rectifying / smoothing circuit 200; a voltage detecting circuit 400 for detecting an output voltage from the rectifying / smoothing circuit 200;
An error amplifier 300 for amplifying an error between the voltage detected at 00 and a reference voltage (hereinafter referred to as E) 11 and a rectifying / smoothing circuit connecting between one end and the other end of the T100 through a leakage inductance (hereinafter referred to as l) 15 of l ₂ 14. 500, a three-terminal regulator (hereinafter 3TR) 20 connected between the output terminals of the rectifying / smoothing circuit 500, capacitors (hereinafter C) 21 and Rp32 connected in parallel to the output terminals of the 3TR, and an output voltage from the rectifying / smoothing circuit 500. Voltage detection circuit 70 for detecting
0, a comparator 600 for comparing the voltage detected by the voltage detection circuit 700 with E24, and a saw-tooth wave signal frequency-modulated with respect to a preset center frequency by an output voltage from the comparator 600. The frequency modulation circuit (hereinafter referred to as FM) 22 and the output of the error amplifier 300 and the output of the FM 22 provide a transistor (hereinafter referred to as T
R) 2 and a PWM control circuit 9 for controlling the width and cycle of the switching.

[0015] The T100 is a l ₁ 3, and l ₂ 4, l ₂ 14
And l ₁₅ . Input circuit 110 includes a C ₁ contacting one end to one end of l _1, the emitter base collector to the other end of the l ₁ to the output terminal of the PWM control circuit 9 and a TR2 to connect the other end of the C ₁ I have.

The rectifier circuit 200 includes a diode (D) 5 to connect the anode to one end of the l ₂ 4, the anode l ₂
D6 connecting the cathode to the cathode of D5 at the other end of D4
When connecting one end and a choke coil having a characteristic inductance is changed by passing current to be connected to the connection point between D5 and 6 (hereinafter L), the other one end to the output end of L7 to the other end of the l ₂ 4 C8.

The voltage detection circuit 400 includes resistors (hereinafter referred to as R) 12 and 13 connected in series between the connection point between L7 and C8 and the ground.
And

The error amplifier 300 has an operational amplifier (hereinafter referred to as AMP) 10 for amplifying the voltage difference between E11 and the voltage at the connection point between R12 and R13, and E11.

The rectifying / smoothing circuit 500 includes a rectifying / smoothing circuit 200
D16, D17, L18, C18
19.

The voltage detecting circuit 700 has a connection point between L18 and C19 and R25 and 26 connected in series between the earth and the ground.

The comparator 600 compares the voltage difference between the voltage at the connection point between R25 and R26 and E24, and AMP23,
24.

FIG. 2 is a diagram showing an example of a frequency characteristic of an output voltage waveform with respect to an input voltage of the frequency modulation circuit according to the embodiment. FIG. 3 is an example of an output voltage waveform with respect to two inputs of the PWM control circuit according to the embodiment. FIG.

Referring to FIG. 2, the FM 22 in this embodiment is
Is the output voltage b due to the increase of the input voltage from the AMP23.
Has the characteristic that the frequency of the waveform becomes higher.

In FIG. 3, in the PWM control circuit 9 in the present embodiment, the width of the output voltage C is determined by the width of the input voltage b obtained by slicing the input voltage b from the FM 22 by the input voltage a from the AMP 10. Function.

FIG. 4 is a diagram showing the output voltage waveform at the steady state on the secondary winding (l ₂ ) 14 side of the transformer in this embodiment. FIG. 5 is a diagram showing the secondary winding (l ₂ ) of the transformer in this embodiment. 14
FIG. 7 is a diagram showing an output voltage waveform when a load on the side changes.

Next, the operation of this embodiment will be described with reference to FIGS.

FIG. 4 shows the voltages V1 and V15 of l2 14 and l15 and the input voltage V3 to the rectifying and smoothing circuit 500, assuming that the load of the output 1 shown in FIG. Is the period of the voltage blocked by T02 and l15, and the input voltage V to the rectifying and smoothing circuit 500 is τ.
When 3 of the duration of positive region and T0N, T0N = T02-τ becomes, when one cycle of the switching waveform of V1 and T0, the input voltage VIN of 3TR20 VIN = V 1 × (T02 -τ) / T0 ... (1)

Next, the load is varied in the output 1, if the output voltage of the output 1 has decreased, the voltage difference between the detection voltage and E ₁₁ of the voltage detection circuit 400 decreases, as shown in FIG. 3 , the output a of APM10 is fed back to the PWM control circuit 9 acts to lengthen the pulse on-time T due to the turn-on of the TR _2, the pulse width of the V _1, V ₃ as shown in FIG. 5 becomes wider The output of l ₂ 14 to the rectifying / smoothing circuit 500 rises. (T ₁₂ > T ₀₂ , T _0Na > T _0N ) As a result, the detection voltage of the voltage detection circuit 700 increases, the voltage difference from E24 increases, and the voltage returns to the FM22.

The FM 22 works in the direction of increasing the frequency (= switching frequency) of the output voltage waveform when the input voltage increases according to the characteristics shown in FIG. The output voltage b of the FM 22 having the increased frequency is fed back to the PWM control circuit 9 so as to shorten the ON period T of the pulse due to the turning on of TR2 as shown in FIG. The output voltage to 500 is lowered and stabilized. Also,
The input voltage of 3TR20 is apparent from equation (1).
Since τ is a constant value, the change in T02 due to the load change
The ratio between T0N and T0 should be constant even if
Is controlled to a constant value.

As described above, the input of the 3TR 20 is stabilized by changing the switching frequency of the TR 2 even if the load voltage of the output 1 changes. Further, even when the output voltage of the 3TR 20 increases, the output of the rectifying / smoothing circuit 500 is stabilized as in the case where the input voltage of the 3TR 20 fluctuates.

As described above, in this embodiment, the voltage of the output 1 is feedback-controlled by the PWM control circuit 9, and the voltage of the output 2
The input voltage of the TR 20 is controlled by feedback through the FM 22, and the L 7 in the rectifying / smoothing circuit 200 has a characteristic that the inductance is larger at the load current in the no-load state than at the steady-state load current. Therefore, since the output 1 is connected to the Rp 31, both the output voltages of the output 1 and the output 2 can be stabilized even when the output 1 is not loaded.

Further, since the input voltage of the 3TR 20 is not affected by the change of the load current and is always controlled to a constant value, the voltage difference between the input and output of the 3TR 20 can be reduced, thereby providing a highly efficient power supply. be able to.

[0033]

As described above, according to the present invention, the switching voltage input to the primary winding of the transformer causes the first secondary winding of the transformer to change its impedance according to the first load current value. of including a first smoothing circuit elements
Having a first DC voltage to generate a preset first DC voltage
Output voltage generating means, preset numerical second transformer including a leakage inductance that approximates the secondary winding side to the second load current including the second the second element impedance is varied by Having a smoothing circuit of
A second output voltage generating means through a three-terminal regulator connected to the smoothing circuit to generate a second DC voltage to generate a second DC voltage that is set in advance, the first smoothing times
First and second output voltages of the first path and the second smoothing circuit, respectively.
Voltage control means for controlling a pulse width and a cycle of a switching voltage in accordance with a result of comparison between a voltage detection voltage and a preset reference voltage of each of the first output voltage generation means and the second output voltage generation means Is provided, even if the respective loads of the first output voltage generating means and the second output voltage generating means fluctuate, the load of the first DC voltage and the second DC voltage from the outside is in a no-load state. No signal is received, and each of the first and second smoothing circuits
1, by comparing the detected voltage of the second output voltage with the reference voltage.
Accordingly, there is an effect that the first DC voltage and the second DC voltage can be stabilized.

The third input terminal of the three-terminal regulator
And the reference voltage and the detection voltage of the second output voltage of the second smoothing circuit.
And the second DC voltage is stabilized, so that the voltage between the input and output of the three-terminal regulator can be made smaller than before.
Tree, voltage loss in the three-terminal regulator is reduced,
There is an effect that the power supply can be downsized and the efficiency can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a frequency characteristic of an output voltage waveform with respect to an input voltage of the frequency modulation circuit according to the embodiment.

FIG. 3 is a diagram illustrating an example of a waveform of an output voltage with respect to two inputs of the PWM control circuit according to the embodiment.

FIG. 4 shows a secondary winding (l ₂ ) of a transformer in the embodiment.
It is a figure showing the output voltage waveform at the time of the steady state of 14 side.

FIG. 5 shows a secondary winding (l ₂ ) of a transformer in the embodiment.
FIG. 14 is a diagram showing an output voltage waveform at the time of a load change on the 14 side.

FIG. 6 is a circuit diagram showing a conventional example.

FIG. 7 is a block diagram showing an application example of the conventional example shown in FIG.

[Explanation of symbols]

 1, 8, 19, 21 Capacitor (C) 2 Transistor (TR) 3 Primary winding (l1) 4, 14 Secondary winding (l2) 5, 6, 16, 17 Diode (D) 7, 18 Choke coil ( L) 9 PWM control circuit 11, 24 Reference voltage (E) 12, 13, 25, 26 Resistance (R) 15 Leakage inductance (l) 20 Three-terminal regulator (3TR) 22 Frequency modulation circuit (FM) 31, 32 Dummy resistance (Rp) 100 Transformer (T) 110 Input circuit 200,500 Rectifying / smoothing circuit 300 Error amplifier 400,700 Voltage detection circuit 600 Comparator

Claims (2)

(57) [Claims] 1. A switching voltage input to a primary winding of a transformer is applied to a first secondary winding of the transformer by a first winding.
Preset first circuit having a first smoothing circuit including a first element whose impedance varies according to the load current value of
A first output voltage generating means for generating a DC voltage of the transformer; and an impedance variable by a second load current value on a second secondary winding side of the transformer including a leakage inductance approximate to a preset numerical value. A second smoothing circuit including a second element, a second output voltage generating means for generating a preset second DC voltage via a three-terminal regulator connected to the second smoothing circuit, Detected voltages of the first and second output voltages of the first smoothing circuit and the second smoothing circuit, respectively, and preset values of the first output voltage generating means and the second output voltage generating means, respectively. Switching voltage control means for controlling a pulse width and a cycle of the switching voltage according to a comparison result with a reference voltage, wherein the first output voltage generation means and the second output voltage generation A multi-output power supply device characterized in that the first DC voltage and the second DC voltage are stabilized even when respective loads of the means fluctuate. Both ends of wherein a transformer to have a second secondary winding comprising a leakage inductance of numbers that approximate the preset numerical value as the primary winding and the first secondary winding, said primary winding An input circuit including a switching transistor connected to a terminal of the first secondary winding; a first rectifying / smoothing circuit connected to both terminals of the first secondary winding to rectify and smooth the input voltage; A first dummy resistor connected to an output side, a first comparison circuit that detects an output voltage of the first rectifying and smoothing circuit and outputs a difference between the first reference voltage and a second reference voltage, Rectifies the input voltage by connecting to both terminals of the secondary winding of
Smoothed, and the second rectifying smoothing circuit for constant output voltage on the basis of the leakage inductance, a three-terminal regulator connected to the output side of the second rectifying smoothing circuit, in parallel to the output side of the three-terminal regulator First to connect
A second comparison circuit that detects an output voltage of the second rectifying / smoothing circuit and outputs a difference between the capacitor and a second dummy resistor and a second reference voltage established in advance; A frequency modulation circuit that outputs a signal that is frequency-modulated with respect to a preset center frequency corresponding to an output voltage from the circuit; and the signal output from the frequency modulation circuit and the first signal.
And a pulse width modulation control circuit that performs switching control of the transistor with an output voltage from the comparison circuit .
The first rectifying and smoothing circuit is inducted by the passing current loss.
A first choke coil having a variable resistance;
The rectifying and smoothing circuit of No. 2 has inductance depending on the passing current value.
And a second choke coil that varies .