JPS63287361A - Primary side circuit for inverter - Google Patents

Abstract

PURPOSE:To improve efficiency at a high speed, by using a switching element having withstand voltage equal to or lower than line voltage, as the primary side switching element of an inverter. CONSTITUTION:The primary side circuit of an inverter is provided with the primary side power source 100 of a transformer 102, an oscillation circuit 101, and transistors(Tr) 103-104, and current is fed to a load from the secondary side of said transformer 102. Then, induction elements 108-109 connected to a space between the first-second Tr 103-104, energized electrically to the primary winding 105 of the transformer 102 when they are together in a conductive state, and connected to both the ends of the primary winding 105 when they get non-conductive attract a counterelectromotive force generated on the primary winding 105. As a result, voltage applied to the first-second Tr 103-104 can be suppressed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to, for example, a primary side circuit of an inverter such as a switching regulator, and particularly relates to a primary side circuit of an inverter such as a switching regulator. The present invention relates to a primary side circuit of an inverter that reduces the amount of noise.

[Prior Art] The configuration of the primary side circuit of a conventional inverter is shown in FIG. 4(A), and its timing diagram is shown in FIG. 4(B). here 50
0 is a pulse signal that turns on and off the transistors 501 and 502, and is input to the bases of the transistors 501 and 502. When the pulse signal 500 rises now (timing T1 in FIG. 4(B)), the transistor 501
and 502 are turned on at the same time, and a current i flows through the primary winding 504 of the transformer 503. flows. Next, the pulse signal 50
0 falls, the transistors 501 and 502 are turned off at the same time (timing T2), and a voltage corresponding to the ratio of the number of turns between the primary winding 504 and the secondary winding 505 is applied across the secondary winding 505 of the transformer 503. Occur.

When both the transistor 501 and the transistor 502 are in the off state, the induced voltage generated in the primary winding 504 causes the diode 506, the primary winding 504, and the diode 5 to
A current flows through the path 07 from the common side of the power supply Vl toward the positive side. At that time, the diodes 506 and 507 are in a conductive state, so the voltage across them is only the forward voltage drop, the emitter potential of the transistor 501 is approximately Ov, and the collector potential of the transistor 502 is approximately equal to the power supply voltage value ■1. Become.

[Problems to be Solved by the Invention] However, when the transistors 501 and 502 are in the OFF state, the voltage between the electrodes of the transistors 501 and 502 shown at 510 in FIG. It is difficult to suppress the voltage to 100%, and it is necessary to use a switching element having a withstand voltage at least twice as high as the primary power supply voltage.

Therefore, if the primary side circuit of an inverter is constructed using such transistors with high withstand voltage, it will not only increase the cost but also increase power loss and reduce the efficiency of the power supply.
There were problems such as a decrease in switching speed.

The present invention has been made in view of the above conventional example, and uses a switching element having a withstand voltage at least lower than the power supply voltage as a switching element on the primary side of an inverter.
The purpose is to provide a high-speed and efficient primary side circuit of an inverter.

[Means for Solving the Problem] In order to achieve the above object, the primary side circuit of the inverter of the present invention has the following configuration. That is, the primary winding of the transformer is connected between the first and second switching elements and is energized when both the first and second switching elements are in a conductive state, and both ends of the primary winding and the two inductive elements connected between the primary power source of the transformer, an oscillation circuit that switches the first and second switching elements almost simultaneously, and the first and second switching elements in a non-conducting state. At this time, a circuit is provided that conducts current from the common side of the primary power source to the power supply voltage side via the two induction elements by the back electromotive force generated in the primary winding.

[Function] In the above configuration, it is connected between the first and second switching means, and when both the first and second switching means are in a conductive state, the primary winding of the transformer is energized, and the first and second switching means are connected. Second
When the switching means becomes non-conductive, the back electromotive force generated in the primary winding is absorbed by the inductive element connected to both ends of the primary winding, and the voltage applied to the first and second switching elements is suppressed. works.

[Embodiments] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[Basic explanation of the configuration of the primary side circuit of the inverter (FIGS. 1 and 2)] FIG. 1 is a simplified basic configuration diagram of the primary side circuit of the inverter according to the embodiment.

In the figure, 100 is the primary side power supply of the transformer 102, and its power supply voltage is Vc. The oscillation circuit 101 is a power supply 100
Oscillation is started at the same time as the transistors 103 and 104 are turned on, and pulse signals having the same timing are output to the transistors 103 and 104. This oscillation circuit 101 may be configured to change the oscillation frequency in response to the output voltage on the secondary side of the transformer 102.

103 and 104 both indicate switching elements, and although they are represented by transistors here, other switching elements such as FETs may be used.

When the pulse signal from the oscillation circuit 101 rises, transistors 103 and 104 are simultaneously turned on (conducting state).
Therefore, current flows through the primary winding 105 of the transformer 102. Next, when the pulse signal from the oscillation circuit 101 falls, the transistors 103 and 104 are simultaneously turned off (non-conductive). As a result, induced voltage is generated in the primary windings 105, 108, and 109, and the transformer 102
Current flows through the secondary winding of transformer 102, and an output voltage is generated on the secondary side of transformer 102.

On the other hand, on the primary side of the transformer 102, the primary winding 105.10
8 and 109 causes a current to flow from the common side of the primary power source 100 through the diode 107, the coil 10B, the primary winding 105, the coil 109, and the diode 110.

At this time, if the coil 108 is not present, the transistor 1
If the voltage drop in the forward direction of the diode 107 is ignored, the emitter of the transistor 04 becomes approximately Ov, and the collector-emitter voltage of the transistor 104 at this time is equal to the voltage of the primary power supply 1.
It becomes almost equal to the power supply voltage of 00, and becomes approximately Vc. However, by providing the coil 108 as in the circuit of the embodiment, the reverse voltage v1 of the coil 108 generated when the transistors 103 and 104 are turned off causes the transistor 104 to
The emitter of is pushed up to the +Vc side by v1'', and the collector-emitter voltage when the transistor 104 is off becomes Vc - V1.

If the coil 109 is not present, the collector voltage of the transistor 103 will be approximately Vc if the forward voltage effect of the diode 110 is ignored, and the collector-emitter voltage of the transistor 103 when it is off will be approximately Vc. However, as in the circuit of the embodiment, the coil 109 is connected to the primary winding 10.
5 and the + side of the power supply, when transistors 103 and 104 are off, the collector voltage of transistor 103 is The collector-emitter voltage of the transistor 103, which is lowered by "V2" from the power supply voltage +Vc and rises when it is off, becomes Vc - V2.

Figure 2 shows the voltage waveforms of each part in Figure 1 and the coil 108.1.
10 is a diagram showing a voltage waveform between the collector and emitter of the transistor 103 when there is no transistor 09. FIG.

In FIG. 2, reference numeral 20 indicates a pulse signal output from the oscillation circuit 101, and reference numeral 21 indicates a voltage waveform between the collector and emitter of the transistor 103 when the coil 108.1.9 is not present. 24 indicates the time during which both transistors 103 and 104 are in an on state, and 25 indicates a time during which both diodes 107 and 110 are conductive due to the back electromotive force induced in the primary winding 105. In this way, the coil is 1°8
．． Without 109, the collector of transistor 103
The emitter voltage VCe rises to the power supply voltage. 26 indicates the time during which both transistors 103 and 104 are in the off state.

22 shows the voltage waveform between the collector and emitter of the transistor 103 in the circuit of FIG.
It is the value obtained by subtracting the reverse voltage V2 of the coil 109. Similarly, 23 indicates the voltage waveform between the collector and emitter of the transistor 104 in the circuit of FIG. Since the voltage of the transistor 104 is pushed up from the Vc side by Vl, this voltage is also lower than the power supply voltage, similar to the voltage value indicated by 22, and the maximum value is Vc-Vl.

[Explanation of an actual power supply circuit (Figure 3)] Figure 3 is a diagram showing an example of an actual power supply circuit.It is an example of a power supply circuit that manually generates an AC voltage of 80 to 250V and outputs +5V6A.
The numbers attached to capacitors, coils, etc. indicate their respective resistance values and capacitances of the capacitors.

When the AC power source is manually supplied, a DC voltage obtained by rectifying the AC voltage is input to the DC-DC converter 35, and power is supplied to the switching circuit 33.

As a result, the switching circuit 33 starts a switching operation, and the transformer 32 inputs pulse signals of the same phase to the bases of the transistors Q1 and Q2. In this way, transistors Q1 and Q2 are controlled to turn on and off simultaneously.

When transistors Q1 and Q2 turn on, transformer 3
Current flows through the primary winding L1 of 4. Next, transistor Q
When l and Q2 turn off at the same time, the primary windings L1 and L2
A back electromotive force is generated in L3 and D1, which causes a diode D1. Coil L
2. Current flows through the primary winding L1, coil L3, and diode D2, and the voltage between the collectors and emitters of the transistors Q1 and Q2 is suppressed below the power supply voltage, as shown at 22.23 in FIG.

Further, in carrying out this operation, the same effect can be obtained by using another transformer.

That is, the primary winding of another transformer is inserted in series in the path of current flowing when both transistors are in the on state,
The same effect is obtained by placing the two secondary windings in the same position as the windings 108, 109 of the transformer 102.

The switching circuit 33 inputs the output voltage of the secondary side of the transformer 34, and controls the on/off frequency of the transistors Q1 and Q2 in response to fluctuations in the output voltage, thereby stabilizing the output voltage. I'm trying.

As described above, according to this embodiment, the primary side of the transformer
Since the maximum voltage between the collector and emitter and between the collector and base of each transistor is suppressed below the power supply voltage value, it is possible to use a transistor with high switching speed, high efficiency, and low breakdown voltage. Therefore, it is possible to create a low-cost, highly efficient power supply circuit with less loss during switching.

[Effects of the Invention] As described above, according to the present invention, it is possible to use a switching element having a withstand voltage lower than the power supply voltage as the primary side switching element.
This has the effect of providing the primary side circuit of the inverter.

[Brief Description of the Drawings] Fig. 1 is a diagram showing a simplified configuration of the primary side circuit of the inverter according to the embodiment, and Fig. 2 shows the timing of each part of the circuit in Fig. 1, and the collector of a temporary transistor without a coil. Figure 3 is a diagram showing an example of the power supply circuit of the embodiment; Figure 4 (A
) is a diagram showing the configuration of a primary side circuit of a conventional inverter, and FIG. 4(B) is a diagram showing timing waveforms of various parts of the primary side circuit of a conventional inverter. In the figure, 31.32... Oscillation circuit, 33... Switching circuit, 100... Power supply, 101... Oscillation circuit,
34.35...DC-DC converter, 102...
Transformer, 103.104... Switching element (transistor), 105-... Primary winding, 106... Secondary winding, 107.110... Diode, IOA, 10
9...It is a coil. Figure 2

Claims (1)

[Claims] a primary winding of a transformer connected between a first and a second switching element and energized when both the first and second switching elements are in a conductive state; two inductive elements connected between a primary power source, an oscillation circuit that switches the first and second switching elements almost simultaneously, and when the first and second switching elements are in a non-conducting state. , a circuit that conducts current from a common side of the primary power source to a power supply voltage side via the two induction elements by a back electromotive force generated in the primary winding.