JPH025677Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a transistor inverter with a low input voltage, and particularly to a transistor inverter having a rectifier circuit suitable for making the inverter inexpensive and highly reliable.

[Background of the idea]

In a conventional transistor inverter, a diode bridge is used in the rectifier circuit as shown in FIG. Therefore, the DC voltage immediately after the power is turned on is highest when the power is turned on immediately before the AC voltage reaches its maximum value. As shown in FIG. 2, in this case, the energy stored in the choke coil is released at the start of oscillation due to simultaneous conduction of the two transistors immediately after the power is turned on, resulting in an overshoot of the collector voltage. This has resulted in the disadvantage that a transistor with a withstand voltage higher than the collector voltage in a steady state must be used. In particular, when the power supply voltage is low, the transistors used in the inverter must have a large current capacity and a high withstand voltage, which is a factor that increases the price.

[Purpose of invention]

An object of the present invention is to provide an inexpensive transistor inverter.

[Summary of the idea]

If the power supply voltage is low, the current capacity of the transistor used in the inverter increases, which increases the price, so it is advantageous to boost the power supply voltage. If a voltage doubler rectifier circuit as shown in FIG. 3 is used for boosting the voltage, the DC voltage after the power is turned on increases every half cycle of the AC voltage and reaches a steady state as shown in FIG. At this time, oscillation starts in the first half cycle, that is, when the DC voltage is half of the steady state. Therefore, there is no need to consider the withstand voltage margin due to overshoot of the collector voltage at the start of oscillation, and it is sufficient to satisfy the withstand voltage in a steady state, making it possible to use a transistor with a low withstand voltage.

[Example of idea]

An embodiment of the present invention will be described below with reference to FIG.

Diode 51 supplies charge to capacitor 53 during the positive half cycle, and diode 52 supplies charge to capacitor 54 during the negative half cycle. The rectified DC current flows through one of the transformer 66 through the chiyoke coil 55 as the transistors 60 and 61 become conductive and non-conductive alternately.
It flows alternately to the next windings 63 and 64. The current flowing through the primary winding generates a potential difference in the feedback winding 65 due to resonance between the resonant capacitor 62 and the primary winding, which causes negative feedback to the base of the transistor that was conducting, and causes a difference in the potential of the transistor that is not conducting. Positive feedback is provided to the base, inverting the transistor. Resistor 56 supplies charge to capacitor 57 and resistor 58
and 59 supply the charge stored in capacitor 57 to transistors 60 and 61 as base current. This generates a high frequency voltage in the secondary winding 67 of the transformer 66.

Now, if the power is turned on during the positive half cycle of the AC power supply, the capacitor 53 is charged through the diode 51 during this positive half cycle, and the capacitor 53 is charged through the diode 51 during the next negative half cycle.
4 is charged through the diode 52, and thereafter, the rectified DC voltage becomes the sum of the charging voltages of the capacitor 53 and the capacitor 54, and becomes a steady state.
Oscillation then begins in the first positive half cycle. Therefore, when the energy stored in the chiyoke coil 55 is released at the start of oscillation due to simultaneous conduction of the two transistors and an overshoot of the collector voltage occurs, the DC voltage is half the voltage in the steady state. Therefore, it is sufficient that the transistor has a breakdown voltage that satisfies the breakdown voltage in a steady state, and there is no need to take collector voltage overshoot into consideration. Furthermore, since the rectified voltage is doubled, the current capacity of the transistor can be reduced. Therefore, inexpensive transistors can be used. Furthermore, in the case of a bridge, the loss due to diodes during rectification is 2 to 3 V because the current always flows through two diodes, which is a large proportion of the loss for a low-voltage power supply, but in this example, the loss is the same as that of one diode. As a result, the loss rate can be reduced and efficiency can be improved.

[Effect of idea]

According to the present invention, the DC voltage after rectification increases every half cycle of AC input, and at the start of oscillation, the voltage is half of the steady state voltage, so there is no effect from collector voltage overshoot, and the transistor has a low breakdown voltage. can be used. Therefore, it is possible to obtain a transistor inverter that is inexpensive and has sufficient reliability.

[Brief explanation of drawings]

Fig. 1 is a conventional circuit diagram, Fig. 2 is a voltage waveform and collector voltage waveform after rectification of the conventional circuit, Fig. 3 is a circuit diagram of an embodiment of the present invention, and Fig. 4 is based on the circuit shown in Fig. 3. A diagram of voltage waveforms and collector voltage waveforms after rectification, and FIG. 5 is a circuit diagram of an embodiment of the present invention. Explanation of symbols, 51, 52... Rectifier diode, 53, 54... Smoothing capacitor, 55... Current limiting choke coil, 56... Base capacitor charging resistor, 57... Base capacitor, 5
8, 59... Base resistor, 60, 61... Transistor, 62... Resonance capacitor, 63, 64
...Primary winding, 65...Feedback winding, 66...Oscillation transformer, 67...Output winding.

Claims (1)

[Scope of utility model registration request] a diode that supplies charge to a capacitor in a positive half cycle, said capacitor that stores the supplied charge, a diode that supplies charge to another capacitor in a negative half cycle, and said capacitor that stores this supplied charge. A voltage doubler rectifier circuit consisting of a voltage doubler rectifier circuit, and two transistors that alternately conduct and non-conduct the DC current supplied by the rectifier circuit to intermittently flow it through a chiyoke coil to the primary winding of the transformer;
A drive circuit that drives these two transistors and a circuit that controls conduction and non-conduction of the two transistors.
A transistor inverter comprising a secondary winding and the transformer, which has a feedback winding for inversion by resonance with a resonant capacitor, and converts a DC voltage into a high-frequency voltage and outputs it by conducting or non-conducting the transistor. A transistor inverter characterized by using a voltage rectifier circuit as a rectifier circuit.