JPH03293965A - Dc power unit - Google Patents

Abstract

PURPOSE:To simplify the construction by connecting a basic output circuit and one or more auxiliary output circuits to the secondary winding of a switching transformer, and controlling the output of said auxiliary output circuit by means of an auxiliary control circuit. CONSTITUTION:A basic circuit comprised of a diode 24, etc., and one or more auxiliary output circuit comprised of a diode, etc., are connected to the secondary winding of a switching transformer 23. The primary winding N1 of the transformer 23 is turned on or turned off by an error amplifier 32, a switching element 22, etc. The output of the auxiliary output circuit is controlled by the on-off of a switching element 30 by means of a comparator 29 and a driving circuit 34. This way, the voltage of load 36 is set lower than the voltage of load 35. Furthermore, the comparator 29 is provided with hysteresis properties. Moreover, the switching frequency of a switching element 30 is set lower than the switching frequency of the switching element 22.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a DC power supply device used as a power source for various electronic devices.

2. Description of the Related Art As a conventional technology, for example, as shown in the circuit diagram of FIG. 5, a switching element 2 is turned on and off to supply power to each output from each winding of a switching transformer 4, thereby generating an uncontrolled output. The voltage varies greatly depending on the load current, and a dropper circuit is required to suppress this variation in output voltage.

The operation of the circuit shown in FIG. 5 will be explained below. When the switching element 2 is turned on by the output of the drive circuit 1, energy is stored in the switching transformer 4 from the DC power supply 3, and when the switching element 2 is turned off, the energy stored in the switching transformer 4 is transferred to each output of the switching transformer 4. They are emitted from the secondary windings of , and are smoothed by a diode 5.10 and a capacitor 6.11 to become a DC voltage.

Furthermore, the output voltage of the load 7 is detected, compared with the reference voltage 8 by the error amplifier 9, amplified, and fed back to the drive circuit 1. This feedback signal controls the on period of the switching element 2 to keep the voltage applied to the load 7 constant.

The transformer winding voltage of the load 12 is determined by the turns ratio with the transformer winding of the load 7, but in reality, leakage magnetic flux occurs in the switching transformer 4, so fluctuations due to the load current cause the transformer winding voltage of the load 12 to change. It will come as a change.

Therefore, the transformer winding voltage of the load 12 is made higher than the set voltage, and the voltage is stepped down by the transistor 13 to supply the load 12 with a DC voltage. Furthermore, the output voltage of the load 12 is detected and compared with the reference voltage 15 by the differential amplifier 14.
By controlling the base current of 3 and always keeping the voltage applied to the load 12 constant, fluctuations in each output voltage are improved. Note that 16 in the figure is a capacitor connected in parallel to the load 12.

Problems to be Solved by the Invention In the conventional circuit as described above, the transformer winding voltage of the load 12 is set higher than the voltage applied to the load 12, and the voltage is stepped down by the transistor 13. Therefore, when the load current is large, the voltage of the transistor 13 is lowered. It has the drawbacks of increased circuit loss, increased size, and increased cost.

The present invention has been made in view of these points, and an object of the present invention is to provide a highly efficient, compact, and inexpensive DC power supply device.

Means for Solving the Problems In order to solve the above problems, the present invention provides a basic rectifying and smoothing circuit for the secondary winding of a switching transformer, which has a primary winding connected to a DC power source via a switching element. One auxiliary output circuit consists of an output circuit, a rectifying and smoothing circuit, an auxiliary voltage detection circuit consisting of a comparator with hysteresis characteristics for detecting the output voltage, and a reference voltage source, and a switching element controlled by this auxiliary voltage detection circuit.
A voltage detection circuit is connected to the above-mentioned basic output circuit, and the voltage detection circuit is configured to control the switching elements on the primary side.

Effect Due to the above circuit configuration, the auxiliary voltage detection circuit performs on/off switching operations of the primary side switching element and the switching element of the auxiliary output circuit asynchronously, and the switching operation of the primary side switching element and the switching element of the auxiliary output circuit is turned on and off by turning on and off the switching element of the auxiliary output circuit. By distributing the energy stored in the switching transformer to each output from the side and using one switching transformer for each output in a time-divided manner, the voltage of each output can be controlled to an arbitrary value.

Example FIG. 1 shows an embodiment of the DC power supply device of the present invention.

The circuit of the present invention is a basic circuit consisting of a rectifying and smoothing circuit composed of a diode 24 and a capacitor 25 in a secondary winding N2 of a switching transformer 23 having a primary winding N1 connected to a DC power supply 21 via a switching element 22. The output circuit includes a rectifying and smoothing circuit consisting of a diode 26 and a capacitor 27, an auxiliary voltage detection circuit consisting of a comparator 29 with hysteresis characteristics for detecting the output voltage, a reference voltage source 28, and a switching element 30 controlled by this auxiliary voltage detection circuit. A voltage detection circuit consisting of a reference voltage source 31 and an error amplifier 32 is connected to the basic output circuit, and the switching element 22 on the primary side is controlled by this voltage detection circuit. It is configured as follows.

In FIG. 1, 33 and 34 are drive circuits, 35 degrees and 36 are loads, and 37 is a bleeder resistor. The voltage applied to the load 36 is set lower than the voltage applied to the load 35. The comparator 29 has a hysteresis characteristic of ΔV2, and if the voltage of the reference voltage source 28 is V2, the auxiliary voltage detection circuit turns the switching element 30 from on to off when the detected voltage reaches the value of Δv2+v2, and the detected voltage becomes the value of v2. When this happens, the switching element 30 operates from off to on. The switching frequency of the switching element 30 is lower than the switching frequency of the switching element 22 (
Set.

When the switching element 30 is on, the switching element 22
is on, power is stored in the switching transformer 23, and when the switching element 22 is off, the load 36
Since the voltage applied to the load 35 is set lower than the voltage applied to the load 35, the diode 24 becomes non-conductive, and all the power stored in the switching transformer 23 is smoothed by the capacitor 27 and supplied to the load 36, and the switching element 22 is Repeat on and off. Further, the switching element 30 is turned on until the output voltage applied to the load 36 is detected and the detected voltage reaches Δv2+v2. At this time, the charging energy of the capacitor 25 is supplied to the load 35.

When the switching element 30 is turned off and the switching element 22 is turned on, power is stored in the switching transformer 23, and when the switching element 22 is turned off,
All the electric power stored in the switching transformer 23 is smoothed by the capacitor 25 and supplied to the load 35, and the switching element 22 is repeatedly turned on and off. Furthermore, load 36
Since the charging energy of the capacitor 27 is supplied to the capacitor 27, the output voltage applied to the load 36 decreases, and the switching element 30 is turned off until the detected voltage reaches V2.

Thereafter, the switching element 30 changes from the off state to the on state, but performs the same operation as described above.

From the above operation, the output voltage applied to the load 36 is kept constant by turning the switching element 30 on and off. load 3
The output voltage applied to the switching element 5 is always kept constant by comparing the detection voltage with the reference voltage 31, amplifying the signal, and controlling the on period of the switching element 22 by a signal fed back to the drive circuit 33.

FIG. 2 shows the waveform of the voltage vs of the secondary winding N2 of the switching transformer 23 and the ripple voltage waveform of the output voltage of the load 35,36. In FIG. 2, V indicates the set voltage of the load 35, V2 indicates the set voltage of the load 36, ΔV1 indicates the ripple voltage of the capacitor 25, and Δv2 indicates the ripple voltage of the capacitor 27. The set voltage v1 of the load 35 becomes the reference voltage of the reference voltage source 31, the set voltage v2 of the load 36 becomes the reference voltage of the reference voltage source 28, and the ripple voltage ΔV2 of the capacitor 27 becomes the hysteresis voltage of the comparator 29. controlled as follows.

The control range is when the switching element 30 is turned on.

During the off period, it is necessary to allow the switching element 22 to turn on one or more times. Also, TONI, TON2,
TOFF2 can be expressed by the following formula.

TON2-哄0 ......(2) 7 (l F p 2-' 2 AV 2-02 ......(3) The above formula (1), (2), (3), In (4), r-p is the reactance of the switching transformer 23, ■ is the DC voltage of the DC power supply 21, C1 is the capacitance of the capacitor 25, C2 is the capacitance of the capacitor 27, ■ old is the load current of the load 35, +02 is The load current of the load 36 is shown.ToNt, TON2, TOF are shown in Fig. 3a and b.
A characteristic diagram according to the load current 1'Of+IO2 of P2 is shown.

In TON2 and TOFF2, formula c2)2 formula (3
), the MAX value is determined as the output current for the load currents I o+ and I 02, so T OH2 and T
opp2 does not go below a certain value. Therefore, when the load current is 101 and the MAX value of I02, TON2
- If TOFF2 is set to a value larger than TON+, the load current will be 101. 102 respectively from no load to M
It becomes possible to control up to AX load. At this time, when the load current 101 is O^, the switching element 30 is always on and the control loop of the switching element 22 is in the oven state, so the bleeder resistor 37 is required for the output of the load 35.

FIG. 4 shows another embodiment of the DC power supply device of the present invention.

The circuit of the present invention is a basic circuit consisting of a rectifying and smoothing circuit composed of a diode 44 and a capacitor 45 in a secondary winding N2 of a switching transformer 43 having a primary winding N1 connected to a DC power supply 41 via a switching element 42. An output circuit, a rectifying and smoothing circuit consisting of a diode 46 and a capacitor 47, an auxiliary voltage detection circuit consisting of a comparator 49 having hysteresis characteristics for detecting the output voltage, and a reference voltage source 48, and controlled by this auxiliary voltage detection circuit. One or more auxiliary output circuits each consisting of a switching element 50 are connected, a voltage detection circuit consisting of a reference voltage source 51 and an error amplifier 52 is connected to the basic output circuit, and this voltage detection circuit detects the switching element 42 on the primary side. The reference voltage is controlled by a comparator 49 having a hysteresis characteristic as the auxiliary voltage detection circuit, a detection circuit 58 for detecting the off period of the switching element 50 of the auxiliary output circuit, and the detection circuit signal. It is composed of a reference voltage source 48.

In FIG. 4, 53, 54 is a drive circuit, 55.degree. 56 is a load, and 57 is a resistor.

Further, the on-period detection circuit 58 works to lower the reference voltage of the reference voltage source 48 when the off-period of the switching element 50 becomes less than a certain time.

Load 55. The control operation of each output voltage applied to the load 56 is the same as the operation of the DC power supply device of the previous embodiment of the present invention.

The off-period TOFF2 of the switching element 50 is expressed by the formula (3
), the capacitance C2 of the capacitor 47 and the hysteresis voltage ΔV2 of the comparator 49 are constant values as circuit constants, and TOFF2 is the current flowing into the load 56! 02
depends only on

As the current roz flowing into the load 56 increases, the off-period TOFF2 of the switching element 50 becomes smaller, and when it becomes less than a certain time, the off-period detection circuit 58 operates and the reference voltage of the reference voltage source 48 is lowered, causing the h load to decrease. The output voltage value applied to the load 56 decreases, and the current 1 (12
is limited, resulting in a protective operation for the current 102.

Effects of the Invention Song As described above, according to the present invention, each output voltage can be controlled without the need for an element that steps down the voltage, which increases loss, and the secondary voltage of the switching transformer can be controlled regardless of the number of outputs. Since there is only one winding, the structure of the switching transformer is simplified, the overall heat generation is reduced, and the reliability of the DC power supply is improved, making it extremely useful.

[Brief explanation of drawings]

Fig. 1 is an electrical circuit diagram of a DC power supply device according to an embodiment of the present invention, Fig. 2 is a voltage waveform diagram of the same main part, and Figs. 3 a and b.
4 is an electrical circuit diagram of another embodiment of the present invention, and FIG. 5 is an electrical circuit diagram of a conventional DC power supply device. 21...DC power supply, 22.30...Switching element, 23...Switching transformer, 24°26...Diode, 25.27.
... Capacitor, 28.31 ... Reference voltage source, 29.32 ... Error amplifier, 33.34
...Drive circuit, 35.36...Load.

Claims (2)

[Claims] (1) The secondary winding of a switching transformer that has a primary winding connected to a DC power supply via a switching element has a basic output circuit consisting of a rectifier and smoothing circuit, a rectifier and smoothing circuit, and a hysteresis characteristic for detecting the output voltage. An auxiliary voltage detection circuit consisting of a comparator with a reference voltage source and a reference voltage source, and one or more auxiliary output circuits consisting of switching elements controlled by this auxiliary voltage detection circuit are connected, and the voltage detection circuit is connected to the above basic output circuit. , a DC power supply device configured to control the switching element on the primary side by the voltage detection circuit. (2) The secondary winding of a switching transformer that has a primary winding connected to a DC power supply via a switching element has a basic output circuit consisting of a rectifier and smoothing circuit, a rectifier and smoothing circuit, and a hysteresis characteristic for detecting the output voltage. An auxiliary voltage detection circuit consisting of a comparator with a reference voltage source and a reference voltage source, and one or more auxiliary output circuits consisting of switching elements controlled by this auxiliary voltage detection circuit are connected, and the voltage detection circuit is connected to the above basic output circuit. , the voltage detection circuit is configured to control the switching element on the primary side, and the auxiliary voltage detection circuit includes a comparator having a hysteresis characteristic, a detection circuit for detecting an off period of the switching element of the auxiliary output circuit, and its detection. A DC power supply device consisting of a reference voltage source whose reference voltage is controlled by circuit signals.