JPS6271475A - Power unit - Google Patents

Abstract

PURPOSE:To obtain a high output by simple and small-sized constitution by adopting construction in which load is supplied with a electromagnetic energy from an inverter transfermer at both ON-OFF of a switching transistor. CONSTITUTION:A switching transistor 12 is ON-OFF operated by an output from a PWM control circuit 22. When the transistor 12 is turned ON, the voltage of a power supply 11 is applied to a primary winding 13p, and voltage generated in a secondary winding 13s1 is fed to a smoothing capacitor 19 through a diode 17 and a choke coil 18. When the transistor 12 is turned OFF, supply voltage is not applied to the primary winding 13p, and voltage generated in a secondary winding 13s2 is fed to the smoothing capacitor 19 through a diode 20 and the choke coil 18. DC voltage is applied to a load 21 from the smoothing capacitor 19 regardless of the transistor 12 being turned ON or OFF.

Description

[Detailed Description of the Invention] Field of Industrial Application] This invention is applicable to the N8! Regarding equipment.

[Prior Art] Conventionally, this type of power supply has been of the 0N-ON inverter type (a type that supplies energy to the secondary side of the inverter transformer when the switching transistor is ON) called the forward type, and the flyback type. 0N-OFF method (when the switching transistor is OFF)
A system in which energy is supplied to the secondary side of an inverter transformer when F is known is known. But 0N-OF
In the F type, electromagnetic energy can only be supplied to the secondary side of the inverter transformer when the switching transistor is turned off, so the transformer utilization efficiency is poor, and the output ripple is large, so the capacity of the smoothing capacitor must be increased. did not become. Furthermore, in order to increase the output capacity, it is necessary to increase the peak current on the primary side of the transformer, which requires increasing the capacity and size of the switching transistor and the transformer. For this reason, the ON-OFF type has a limited capacity, and in practical terms, it can only be about 100 to 200 W at most, and cannot be used in patents that feature a capacity. In this respect, the ON-ON type has a relatively large capacity, and is therefore widely used in power supplies that require a large capacity.

As a conventional power supply device having such an ON-ON type inverter circuit, the one shown in FIG. 3 is known.

In this case, a primary winding 3p of an inverter transformer 3 is connected via a switching transistor 2 to a DC power supply 1 obtained by rectifying a commercial AC II source, for example. The transistor 2 is configured to be switched by the output of the PWM control circuit 4. A smoothing capacitor 7 is connected to the secondary winding 3S of the inverter transformer 3 via a rectifying/diverting diode 5 and a choke coil 6 in series,
A diode 8 is connected in parallel to the smoothing capacitor 7 via the choke coil 6 in the polarity shown. A load 9 is connected to the smoothing capacitor 7.

In this one, switching transistor 2 is ON
Then, a voltage Vp1VB is induced in the primary winding 3p and secondary winding 3S of the inverter transformer 3 in the polarity shown by the arrow.

Since the primary winding 3p and the secondary winding 3S have the same polarity, when the transistor 2 is ON, the electromagnetic energy of the primary winding 3p is transmitted to the secondary winding 3S. This voltage is rectified by a diode 5, passed through a choke coil 6, smoothed by a smoothing capacitor 7, and applied to a load 9. The peak value of the secondary current at this time is the voltage applied to the choke coil 6, which is V L
s If the inductance of the choke coil 6 is L, then (
VL/2L) TON+IO.

However, TON is the ON time of transistor 2, and 10 is a secondary smoothing current.

When the transistor 2 is off, the electromagnetic energy stored in the choke coil 6 is released in the choke coil 6→load 9→diode 8 loop at the instant the transistor 2 is turned off, and a voltage is applied to the load 9. The minimum value of the secondary current at this time is In-(VL/2L)TOPF. However, To F p is the OFF time of the transistor 2.

In this way, in the 0N-ON type, the O
Since this method stores electromagnetic energy in the choke coil 6 when the transistor is turned off and releases it to the load 9 when the transistor 2 is turned off, it is practically recommended that the choke coil 6 has low leakage flux, low loss, and secondary Since magnetic saturation must not occur due to current, a ring core is usually used.

In this way, in the 0N-ON type, the O
It can be seen that since electromagnetic energy is supplied to the load 9 in both N and OFF states, the energy use efficiency is good.

[Problems to be solved by the invention] However, in this conventional 0N-ON system, the choke coil 6
Low-loss, expensive products are used as a transformer, and large products such as inverter transformers are used, which increases the size of the equipment. Therefore, they are not used in products that require miniaturization, such as peripheral equipment for microcomputers. There was a difficult problem.

The present invention was made in order to solve these problems, and its purpose is to provide a power supply device that is compact, provides high output, has a simple configuration, is highly economical, and is useful as a power source for system equipment. shall be.

Means for Solving Problems c] The present invention provides an inverter transformer having a primary winding, a secondary winding of the same polarity as the primary winding, and a secondary winding of the opposite polarity, and a primary winding of the inverter transformer. A switching transistor is connected to the terminal, and the switching operation of the transistor generates a high-frequency output in each secondary winding.
5 types of inverter circuits, a pair of rectifier circuits that rectify the output from each secondary winding, and the output of each rectifier circuit is inputted through a common choke coil, and the output of each rectifier circuit is inputted through a common choke coil. This is a power supply device equipped with a smoothing capacitor that outputs direct current.

[Function] In the present invention having such a configuration, when the switching transistor is ONL, a voltage is generated in the secondary winding of the inverter transformer which has the same polarity as the primary winding, and one of the rectifier circuits. , a voltage is supplied to the load via the choke coil and the smoothing capacitor, and when the switching transistor is turned off, a voltage is generated in the secondary winding with the opposite polarity to the primary winding, and the other rectifier circuit, choke coil, and smoothing capacitor are supplied with voltage. Voltage is supplied to the load via. In this way, electromagnetic energy from the inverter transformer can be supplied to the load both when the switching transistor is turned on and off without relying on the choke coil.

[Example] Embodiments of the present invention will be described below with reference to the drawings.

As shown in FIG. 1, a primary winding 13p of an inverter transformer 13 is connected via a switching transistor 12 to a DC power 1111 obtained by rectifying a commercial AC power source, for example. Primary winding 1i1 of the inverter transformer 13
A parallel circuit of a capacitor 15 and a resistor 16 is connected in parallel to 3p via a diode 14 with the polarity shown.

The inverter transformer 13 includes a secondary winding 11381 having the same polarity as the primary winding 13p and a secondary winding [11381] having the opposite polarity.
Two secondary windings 82 are provided, one of which is connected to a smoothing capacitor 19 via a diode 17 and a choke coil 18 constituting a rectifier circuit, and the other
The smoothing capacitor 19 is connected to 3S2 via the diode 20 and the choke coil 18, which constitute a rectifier path.

A load 21 is connected to both ends of the smoothing capacitor 19.

The switching transistor 12 is a PWM control circuit 2.
The switching operation is performed by 2.

This PWM control circuit 22 has an NPN transistor 24 connected between the power supply terminal and the ground via the primary winding of a transformer 23, and the output of a two-power AND gate 25 is supplied to the base of the transistor 24. has been done. The output from the comparator 26 is input to one input terminal of the AND gate 25, and the triangular wave oscillator 27 is input to the other input terminal.
A triangular wave is input from. The comparator 26 is inputted with the triangular wave from the triangular wave oscillator 27 converted into a sawtooth wave by the sawtooth wave generating circuit 28, and the output of the differential amplifier 29 for 6 seconds.

A reference voltage created by a Zener diode 30 and a voltage from a variable resistor 3'B) are input to the differential amplifier 29. In the embodiment of the present invention having such a configuration in which the variable resistor 31G is connected in parallel with the smoothing capacitor 19, the switching transistor 1
2 is operated in a 0NOFF state with a certain duty ratio by the output from the PWMυ1@circuit 22. When the transistor 12 is ONL, the voltage of the power supply 11 is applied to the primary winding 1113+), which causes one of the secondary windings 13S1 to
．． A voltage Vs1 is generated with the polarity of the arrow shown in the figure, and this voltage V
ss is supplied to a smoothing capacitor 19 via a diode 17 and a choke coil 18. Also transistor 1
2 is 0FFL, no power supply voltage is applied to the primary winding 13p, and a voltage V82 is generated in the other secondary winding 13S2 with the polarity indicated by the arrow, and this voltage Vs2 is passed through the diode 20 and the choke coil 18. Smoothing capacitor 1
9. Since the voltage VB2 at this time is a flyback voltage, the phase is X even if it is delayed by 180°. By repeating such an operation, the voltage waveform shown in FIG. The next volume 11A 13s 1 has a voltage Vs shown in FIG. 2(b)! occurs, and the other secondary winding 13s2
In this case, a voltage Vs2 shown in FIG. 2(c) is generated. Therefore, the smoothing capacitor 19 has (
The voltage shown in d) will be applied. In this way, a DC voltage is applied to the load 21 from the smoothing capacitor 19 even if the transistor 12 is turned on or 0FFL. Note that the voltage V8 generated in the other secondary winding 1382
The magnitude of 2 is determined by the values of the load 21, the primary winding [1131], the ON/OFF duty ratio of the transistor 12, etc., but when the transistor 12 is ON, the value is applied to one of the secondary windings 13S1 Generated voltage Vss
If it is determined that the smoothing capacitor 19 is charged to the same value as that of the above equation, the voltage applied from the smoothing capacitor 19 to the load 21 can be the required voltage.

In this way, the switching transistor 12 is turned on and off.
Since magnetic energy can be used in both F, the utilization rate of the inverter transformer 13 can be increased. In addition, this method differs from the conventional 0N-ON method in that the choke coil 18
Since there is no need to rely on energy emitted from the choke coil 18, a small one with a small number of turns can be used as the choke coil 18.
Furthermore, since high efficiency and low loss are not required, economical efficiency can also be improved. Further, since the choke coil 18 can be made smaller, losses such as iron loss and copper loss can be reduced, and input/output conversion efficiency can be improved. Furthermore, since the loss of the choke coil can be ignored compared to the conventional case in which the voltage of the energy emitted from the choke coil decreases when the transistor 12 is turned off, the smoothing capacitor 19 does not require a large capacity, and in this respect as well, miniaturization can be achieved. I can do it.

Moreover, the voltage V82 induced in the other secondary winding 13B2
is one of the secondary windings 1381 when the transistor 12 is turned on.
This voltage is higher than the voltage Vs1 induced by Vs1, and although it depends on various conditions, the value is about twice as high for the same load. Therefore, the other secondary winding 1382- may be approximately half the size of the one secondary winding 1381, and the amount increased by this secondary winding 13B2 is negligibly small compared to the amount decreased by the choke coil 18.

The table below shows an example of comparison between the conventional 0N-ON method 2 and this embodiment.

This table also shows that the output voltage, output current, and efficiency can be improved compared to the conventional device, and the choke coil can be significantly reduced in size from 75 μH to 10 μH. And the other secondary winding 1!13s2 is 2.25 turns, which is an almost negligible amount.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a power supply device that is small in size, provides output power, has a simple configuration, is highly economical, and is useful as a power source for system equipment.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, FIG. 2 is a voltage waveform diagram of various parts in the same embodiment, and FIG. 3 is a circuit diagram showing a conventional example. 12... Switching transistor, 13... Inverter transformer, 13sr, 1382... Secondary winding, 17.20... Rectifier diode, 18... Choke coil, 19... Smoothing capacitor, 21 ···load.

Claims (1)

[Claims] An inverter transformer has a primary winding, a secondary winding of the same polarity as the primary winding, and a secondary winding of the opposite polarity, and a switching transistor is connected to the primary winding of the inverter transformer, and the switching operation of the transistor is Therefore, a single-stone inverter circuit that generates a high frequency output in each of the secondary windings, a pair of rectifier circuits that rectify the output from each of the secondary windings, and a choke coil that connects the output of each rectifier circuit. 1. A power supply device comprising a smoothing capacitor that outputs smoothed direct current to a load, which is input through a common power source.