JPS598430A - Zero cross control circuit - Google Patents

Abstract

PURPOSE:To obtain an excellent waveform-shaped zero cross signal with a simple circuit constitution, by applying the zero cross signal generated at an output terminal of a control transistor(TR) to a control circuit. CONSTITUTION:A TR10 is biased and turned on, while a voltage of an AC power supply 1 is larger than a voltage of a power supply 6 of a control circuit 5, since a charging current flows to the power supply 6 of the control circuit through a diode bridge 2 and an emitter-base junction of the TR10 from the power supply 1. Further, while the voltage of the power supply 1 is lower than the voltage of the power supply 6 of the control circuit, since the emitter-base junction is biased reverse, the TR10 turns off. Thus, the zero cross signal as the input to the circuit 5 is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a zero-cross control circuit, and more particularly to an electronic circuit that performs control in synchronization with four zero-cross points of an AC power source.

Conventionally, this type of circuit was constructed as shown in FIG. 1, and a zero cross signal was extracted from the output of the diode bridge (power supply voltage (a) in FIG. 2) by resistor division. However, as shown in FIG. 2(b), the output of the diode bridge has a problem in that the voltage at the zero cross point does not become completely zero volts due to the influence of the residual charge of the junction capacitance of the diode.

To solve this problem, conventional circuits either choose a small value for the detection resistor to reduce the discharge time constant of the junction capacitance, or use a waveform shaping circuit using two transistors as shown in Figure 3. I was taking it. However, these methods have the disadvantage that the rated capacity of the resistor increases in the former case, and the number of parts increases in the latter case, which increases the mounting space and cost of the circuit.

The present invention was made in order to solve the above-mentioned drawbacks of the conventional technology, and therefore, an object of the present invention is to provide a novel zero-crossing control circuit that can generate a good zero-crossing signal with a υ waveform shaped by a simple circuit configuration. It is about offering and providing.

The above object of the present invention is to provide a transistor including an input terminal and an output terminal connected to both output terminals of a rectifier circuit, and a control terminal connected to a DC power supply of the control circuit, and a zero-cross signal generated at the output terminal of the transistor. This is achieved by a zero-cross control circuit characterized in that it supplies the control circuit with:

Hereinafter, a preferred embodiment of the present invention will be explained in detail with reference to FIGS. 4 and 5.

FIG. 4 is a circuit configuration diagram showing an embodiment of the present invention. In FIG. 4, elements with the same numbers as in FIG. 1 have the same function as in FIG. 1, i.e. with reference number 1.
2 is an AC power supply, 2 is a diode bridge, 3 is a load, 4 is a control switching element, 5 is a control circuit that supplies a trigger signal to the switching element in synchronization with a zero-cross signal, and 6 is a power supply for the control circuit. Reference numeral 10 denotes a circuit that serves to detect the zero cross point of the AC power source, charge the control circuit power source, and shape the waveform, which are characteristics of the present invention.

With this configuration, during a period when the voltage of the AC power supply 1 is higher than the voltage of the power supply 6 of the control circuit 5, the power supply 6 of the control circuit is connected from the AC power supply 1 through the diode bridge 2 and the emitter base junction of the transistor 10. Since the charging current flows, the transistor 10 is biased and turned on, and during the period when the voltage of the AC power supply 1 is lower than the voltage of the power supply 6 of the control circuit, the emitter-base junction is reverse biased, so that the transistor 10 is turned on. is turned off. Therefore, a zero-cross signal as shown in Figure 5 (C) is obtained as an input to the control circuit 5. In Figure 5, (A) is the AC power supply voltage waveform, and (B) is the diode waveform. The output waveform of the bridge, (c) is the power supply voltage of the control circuit 5, and (c) is the waveform-shaped zero-cross signal.

In this embodiment described above, a bipolar transistor is used as the transistor IO, but instead, F
It is also possible to use unipolar transistors such as ETs. However, in this case, it is necessary to replace the power source 6, which is composed of a constant voltage diode and a capacitor, with a battery or a constant voltage power source.

As described above, according to the present invention, a zero-cross signal can be obtained with a simple circuit configuration, so that the mounting space and cost of the device can be reduced.

[Brief explanation of drawings]

Figure 1 is a diagram showing a configuration example of a conventional zero-cross signal detection circuit, Figure 2 is a diagram showing waveforms of each part of the circuit in Figure 1, and Figure 3 is a diagram showing a configuration example of a conventional zero-cross signal detection circuit.
4 is a diagram showing another configuration example of a conventional zero-crossing signal detection circuit, FIG. 4 is a circuit configuration diagram showing an embodiment of the present invention, and FIG.
The figure is a diagram showing waveforms at various parts in FIG. 4. 110. AC power supply, 20. . Diode bridge, 3.
,. Load, 450. Semiconductor switch element, 500. a control circuit for the semiconductor switch element 4, 6. ,, the power supply of the control circuit 5,
700. Charging circuit for power source 6, 8. , , power supply voltage detection circuit, 900. Waveform shaping circuit, 10. ,, Transistorization for control Patent attorney Yuta Kumagai Figure 3 2

Claims (3)

[Claims] (1) A transistor is provided whose input terminal and output terminal are connected to both output terminals of the rectifier circuit, and whose control terminal is connected to the DC power supply of the control circuit, and the zero-cross signal generated at the output terminal of the transistor is A zero-cross control circuit characterized by supplying power to a control circuit. (2) The transistor is a bipolar transistor, the DC power supply is configured with a parallel circuit of a constant voltage element and a capacitor, and the capacitor is charged from the output of the rectifier circuit via the emitter junction of the bipolar transistor. A zero-cross control circuit according to claim (1). (3) The zero-cross control circuit according to claim (1), further characterized in that the transistor is a unipolar transistor, and the DC power source is a battery or a constant voltage circuit.