JPH089640A - Multioutput power unit - Google Patents

Abstract

PURPOSE:To improve efficiency of a multioutput power unit by stabilizing the output voltage of the power unit against load fluctuation and reducing the loss of a three-terminal regulator. CONSTITUTION:When a load on an output 1 side fluctuates, the voltage of the output 1 is stabilized by means of a PWM control circuit 9. When the load fluctuates, the input voltage VIN of a 3TR (Three-terminal regulator) 20 on an output 2 side also fluctuates, but the input voltage (VIN) of the 3TR 20 is stabilized by equivalently changing the input voltage of a rectifier smoothing circuit 500 on the output 2 side by changing the switching frequency of a TR 2 by means of an FM (frequency modulating circuit) 22 by utilizing that the voltage period inhibited by a leakage inductance (l) 15 is constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a multi-output power supply device,
In particular, it relates to a switching type multi-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 this conventional example.

This conventional example shown in FIG. 6 and FIG.
3-277471 gazette: It is the content described in the "multi-output switching power supply device."

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

When the output voltage V ₁ becomes higher than + 12V,
The voltage division 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 main terminals 54a and 54b become conductive, a current flows to the photodiode PCa of the photocoupler PC through 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 given to the switching oscillation circuit and the MOS FET 42.

The output voltage detection amplifier 54 and the resistors R55 and R56 detect the output voltage Va of the rectifying / smoothing circuit 46 including the diode D2 and the capacitor C2, and when the voltage Va exceeds a predetermined value, the output voltage detection amplifier. 5
The main terminals 54a and 54b of No. 4 are electrically connected to each other and the photocoupler P
The C photodiode PDa is issued. Control input terminals 55c and 54c of the output voltage detection amplifiers 55 and 54 when the transistors Tra and Trb are turned on, respectively.
Of the output voltage detection amplifier 55
And prevents conduction between the main terminals of 54. The control signal CONT is input directly 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 the 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 voltage V ₁ is kept at a predetermined value.

[0009]

This conventional multi-output power supply device stabilizes the output voltage by receiving a control signal for detecting a load condition and a no-load condition from a device to which the conventional multi-output power supply device is applied. However, there is a problem that a detection circuit for detecting a load state and a no-load state must be provided in the applied device.

[0010]

According to the multi-output power supply device of the present invention, a switching voltage input to a primary winding of a transformer causes impedance to a first secondary winding side of the transformer by a first load current value. A second output voltage generating means for generating a preset first DC voltage including a variable first element, and a second secondary of the transformer including a leakage inductance approximating a preset numerical value. Second output voltage generating means for generating a second preset DC voltage via a three-terminal regulator including a second element whose impedance is varied on the winding side by a second load current value; 1 output voltage generating means and the second
Switching voltage control means for controlling the pulse width and cycle of the switching voltage according to the result of comparison with each preset reference voltage of the output voltage generating means.

The multi-output power supply device of the present invention includes a transformer having a primary winding, a first secondary winding, and a second secondary winding including a leakage inductance having a numerical value approximate to a preset numerical value, and An input circuit connected to both terminals of the primary winding and including a switching transistor; a first rectifying and smoothing circuit connected to both terminals of the first secondary winding to rectify and smooth the input voltage; A first dummy resistor connected to the output side of the first rectifying / smoothing circuit and a first dummy voltage that detects the output voltage of the first rectifying / smoothing circuit and outputs a difference between the first reference voltage and a preset first reference voltage. A comparator circuit; a second rectifying / smoothing circuit connected to both terminals of the second secondary winding to rectify and smooth the input voltage; and a three-terminal regulator connected to the output side of the second rectifying / smoothing circuit. , Connected in parallel to the output side of the three-terminal regulator A second comparator circuit for detecting the output voltage of the second rectifying and smoothing circuit and outputting a difference between the first reference voltage and the second reference voltage established in advance; A frequency modulation circuit for outputting a signal frequency-modulated with respect to a preset center frequency corresponding to the output voltage from the comparison circuit; and the signal output from the frequency modulation circuit and the first comparison circuit. A pulse width modulation control circuit that controls switching of the transistor according to an output voltage, the first rectifying / smoothing circuit includes a first choke coil whose inductorless is variable according to a passing current value, and the second rectifying / smoothing circuit. The circuit includes a second choke coil whose inductorless is variable according to the passing current value.

[0012]

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

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

In FIG. 1, the present embodiment is a transformer (hereinafter T) 100, an input circuit 110 connected to both terminals of a primary winding (hereinafter l ₁ ) 3 of T100, and a secondary winding of T100 (hereinafter l). ₂ ) Rectifying and smoothing circuit 200 connected to both terminals of 4
A dummy resistor (hereinafter Rp) 31 connected between the output terminals of the rectifying / smoothing circuit 200, a voltage detecting circuit 400 for detecting an output voltage from the rectifying / smoothing circuit 200, and a voltage detecting circuit 4.
Error amplifier 300 for amplifying the error between the voltage detected at 00 and the reference voltage (hereinafter E) 11 and a rectifying and smoothing circuit for connecting one end and the other end through the leakage inductance (hereinafter l) 15 of l ₂ 14 of T100. 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 that compares the voltage detected by the voltage detection circuit 700 with E24, and a sawtooth wave signal that is frequency-modulated with respect to the center frequency preset by the output voltage from the comparator 600. The frequency modulation circuit (hereinafter, referred to as FM) 22 that operates, and the transistor (hereinafter, referred to as T
R) 2 and a PWM control circuit 9 for controlling the width and cycle of switching.

T100 is l ₁₃ , l ₂ 4 and 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 There is.

The rectifier circuit 200 includes a diode (hereinafter D) 5 for connecting the anode to one end of l ₂ 4 and the anode for l _{2 4.}
D6 connecting the cathode to the cathode of D5 at the other end of 4
And a choke coil (hereinafter L) having the characteristic that the inductance is changed by the passing current connecting one end to the connection point of D5 and 6, and connecting one end to the output end of L7 and the other end to the other end of l ₂ 4 C8 and

The voltage detection circuit 400 has resistors (hereinafter R) 12 and 13 connected in series between the connection point of L7 and C8 and the ground.
And have.

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

The rectifying / smoothing circuit 500 is a rectifying / smoothing circuit 200.
D16, D17, L18, and C with the same circuit configuration as
19 and 19.

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

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

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

In FIG. 2, the FM 22 in this embodiment
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 high.

In FIG. 3, in the PWM control circuit 9 of this 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 with the input voltage a from the AMP 10. It has the function of

FIG. 4 is a diagram showing a steady-state output voltage waveform on the secondary winding (l ₂ ) 14 side of the transformer in this embodiment, and FIG. 5 is a secondary winding (l ₂ ) of the transformer in this embodiment. 14
It is a figure which shows the output voltage waveform at the time of the load change of the side.

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

FIG. 4 shows the voltage V ₁ of l ₂ 14 and the voltage V _{2 of} l ₁₅ and the input voltage V to the rectifying / smoothing circuit 500 when the load of the output 1 shown in FIG. 1 has a constant value. ₃ , the period of the positive region of V ₁ is T ₀₂ , the period of the voltage blocked by l ₁₅ is τ, and the input voltage V to the rectifying and smoothing circuit 500 is V.
_When the period of the positive region of ₃ is T _0N , T _0N = T _{02 −τ} , and when one cycle of the switching waveform of V ₁ is T ₀ , the input voltage V _{IN of} 3TR20 is V _IN = V ₃ × ( T ₀₂ −τ) / T (1)

Next, when the load of the output 1 changes and the output voltage of the output 1 decreases, the voltage difference between the voltage detected by the voltage detection circuit 400 and E ₁₁ becomes small, as shown in FIG. In addition, the output a of the APM 10 is fed back to the PWM control circuit 9 to work to prolong the ON period T of the pulse due to ON of TR ₂ , and the pulse widths of V ₁ and V ₃ also become wider as shown in FIG. 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 rises and the voltage difference from E24 increases, and the voltage is fed back to the FM 22.

According to the characteristics shown in FIG. 2, the FM 22 works in the direction of increasing the frequency (= switching frequency) of the output voltage waveform when the input voltage increases. Output voltage b of FM22 which the frequency becomes higher is fed back to the PWM control circuit 9, a pulse of the ON period T by TR2 ON, serves to shorten, as shown in FIG. 3, the rectifying and smoothing of l ₂ 14 The output voltage to the circuit 500 is lowered and stabilized.

As described above, the input of the 3TR20 is stabilized by changing the switching frequency of the TR2 even if the load voltage of the output 1 changes. Even when the output voltage of the 3TR20 rises, the output of the rectifying / smoothing circuit 500 is stabilized as in the case where the input voltage of the 3TR20 changes.

As described above, in this embodiment, the voltage of the output 1 is fed back and controlled by the PWM control circuit 9, and the output 2 3
The input voltage of TR20 is fed back and controlled by the FM22, and L7 in the rectifying / smoothing circuit 200 has a characteristic that the load current in the no load state has a larger inductance than that in the steady load current. Therefore, since Rp31 is connected to the output 1 side, both output voltages of the output 1 and the output 2 can be stabilized even when the output 1 side is unloaded.

Since the input voltage of the 3TR20 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 3TR20 can be made small, thus providing a highly efficient power source. be able to.

[0033]

As described above, according to the present invention, the impedance changes from the switching voltage input to the primary winding of the transformer to the first secondary winding side of the transformer according to the first load current value. First output voltage generating means for generating a preset first DC voltage including the element of
It is preset through a three-terminal regulator that includes a second element whose impedance is variable according to a second load current value on the second secondary winding side of a transformer that includes a leakage inductance that approximates a preset numerical value. Second output voltage generating means for generating a second DC voltage for generating a second DC voltage, and preset reference voltages for the first output voltage generating means and the second output voltage generating means, respectively. By including the switching voltage control means for controlling the pulse width and the cycle of the switching voltage according to the comparison result of 1., even if the respective loads of the first output voltage generating means and the second output voltage generating means change. First from the outside
There is an effect that the first DC voltage and the second DC voltage can be stabilized without receiving the signals in the no-load state for the DC voltage and the second DC voltage.

Further, since the voltage between the input and output of the three-terminal regulator can be made smaller than in the conventional case, the voltage loss in the three-terminal regulator becomes small, and there is an effect that the power supply can be downsized and the efficiency can be improved.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an example of frequency characteristics of an output voltage waveform with respect to an input voltage of the frequency modulation circuit in the present embodiment.

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

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

FIG. 5 is a secondary winding (l ₂ ) of the transformer in this embodiment.
It is a figure which shows the output voltage waveform at the time of load change at 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 and smoothing circuit 300 Error amplifier 400,700 Voltage detection circuit 600 Comparator

Claims (4)

[Claims] 1. A switching voltage input to a primary winding of a transformer is first applied to a first secondary winding side of the transformer.
Of the transformer, the first output voltage generating means including a first element whose impedance varies according to the load current value of 1 to generate a preset first direct-current voltage, and the leakage inductance approximating a preset numerical value. Second preset DC voltage is generated via a three-terminal regulator including a second element whose impedance is changed by the second load current value on the second secondary winding side of the second
Controlling the pulse width and cycle of the switching voltage according to the result of comparison between the output voltage generating means and the preset reference voltage of each of the first output voltage generating means and the second output voltage generating means. Switching voltage control means for controlling the first DC voltage and the second DC voltage even if the respective loads of the first output voltage generating means and the second output voltage generating means fluctuate. A multi-output power supply device characterized in that 2. A transformer having a primary winding, a first secondary winding, and a second secondary winding including a leakage inductance having a numerical value approximate to a preset numerical value, and both ends of the primary winding. An input circuit which is connected to the child and includes a switching transistor; a first rectifying and smoothing circuit which is connected to both terminals of the first secondary winding to rectify and smooth the input voltage;
Comparing the first dummy resistor connected to the output side of the rectifying / smoothing circuit with the first dummy resistor and outputting a difference between the output voltage of the first rectifying / smoothing circuit and a preset first reference voltage. A second rectifying / smoothing circuit connected to both terminals of the second secondary winding to rectify and smooth the input voltage; a three-terminal regulator connected to the output side of the second rectifying / smoothing circuit; Outputs the difference between the first capacitor and the second dummy resistor connected in parallel to the output side of the three-terminal regulator and the second reference voltage established in advance by detecting the output voltage of the second rectifying and smoothing circuit. And a frequency modulation circuit that outputs a signal that is frequency-modulated with respect to a preset center frequency corresponding to the output voltage from the second comparison circuit, and the frequency modulation circuit that outputs the frequency modulation signal. Whether the signal and the first comparison circuit Multiple-output power supply unit, characterized in that it comprises a pulse width modulation control circuit for controlling switching of the transistor output voltage and by the. 3. The multi-output power supply device according to claim 2, wherein the first rectifying / smoothing circuit includes a first choke coil whose inductorlessness varies depending on a passing current value. 4. The multi-output power supply device according to claim 2, wherein the second rectifying / smoothing circuit includes a second choke coil whose inductorless is variable depending on a passing current value.