JPH0693942A - Capacitor charge discharge type ignition device - Google Patents

Abstract

PURPOSE:To reduce incurring of a switching loss and maintain a switching frequency at a high value by cutting off a switching element through detection of the primary current of a transformer. CONSTITUTION:A capacitor C2 is charged with an output from an RCC type converter 1 and the charge is discharged to an ignition coil through a thyristor S1 to perform ignition. In this case, the primary current of a transformer T1 is detected in a ratio, proportioning an input voltage, by a circuit 3a by means of a resistor R3 to output an output signal. When the secondary output voltage of the transformer T1 is increased to a value higher than a specified value, an output signal is detected by the circuit 3c, and an ignition state is detected by a circuit 3d to output a signal. Switching of the converter 1 is stopped by a circuit 3b by means of output signals from the circuits 3a, 3c, and 3d. Further, a battery voltage is detected by a circuit 3e to perform the stop of switching of the converter 1. This constitution causes reduction of incurring of a switching element loss and the increase of a switching frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a capacitor charging / discharging type ignition device using a ringing choke type converter (RCC), and more particularly to control of an oscillating switch element forming a converter.

[0002]

2. Description of the Related Art As an engine ignition device, a battery voltage is boosted through a converter, a capacitor is charged by this voltage, and a discharge thyristor is ignited by a pulse sent from a timing pulse generating coil. A charging / discharging type ignition device for capacitors, which discharges the electric charge of a capacitor to an ignition coil to ignite a plug by giving the electric charge, is widely used. By the way, this device is configured as shown in FIG. 1, and a bipolar transistor Q1 is used as a switching element, and a transistor Q1 is used.
Since the switching is performed by using the unsaturation of 1 and cutting off, there is a drawback that the loss of the transistor Q1 increases and the switching frequency cannot be increased.

[0003]

It is an object of the present invention to reduce the loss of the switching element used in the RCC converter and to increase the switching frequency, to reduce the size of the transformer and to reduce the input low voltage. The purpose is to provide data.

[0004]

The present invention provides RC
MOS as a main switching element that constitutes a C-type converter
Type transistor (MOSFET) is used and the M
The OSFET includes an input voltage detecting means, a converter input current detecting means, an output voltage detecting means, and an ignition state detecting means.
It is configured to be controlled by one means.

[0005]

2 is a circuit diagram of an embodiment of the present invention, FIG.
Is a waveform diagram for explaining the operation, 1 is a DC converter configured by the RCC method, and 2 is a basic circuit of the CD 1. Three
a is the resistance R for the primary current of the transformer T1 of the DC converter
A circuit for outputting an output signal by detecting at a ratio proportional to the input voltage in 3 and a circuit for outputting an output signal when the secondary output voltage of the transformer of the DC converter becomes a certain value or more, 3c is an ignition state Circuit 3b for detecting
A circuit for stopping switching of the DC converter by an output signal from the circuit of d, 3e is a battery voltage (input voltage)
Is a circuit for detecting the above and stopping the switching.

Next, to operate this, a DC power supply voltage is supplied from the battery, and the initial starting resistor R1 and the Zener are supplied.
By applying a voltage across G-S of the FET Q1 through the diode Z4, the primary side n1 of the transformer T1 is turned on by the FET Q1.
N, and along with it, from the auxiliary winding nf, G of FET Q1
Further voltage is applied between S. Further, as shown in FIG. 3 (a), the ON current on the primary side is detected by a value determined by the division ratio of the resistor R3, the comparator IC1 and the resistors R4, R5, and when it exceeds this value, FIG. 3 (b) At the same timing as the above, FET Q1 is turned on by turning on transistor Q2 from comparator IC1.
G-S is cut off and the FET Q1 is turned off.
As a result, the primary current of the transformer T1 stops flowing, and the output of the auxiliary winding nf changes from the positive bias to the reverse bias between G and S of the FET Q1 as shown in FIG.
Keep the cutoff of FET Q1. At that time, the secondary n2 output of the transformer T1 passes through the diode D1 and
The main capacitor-C2 is charged. As the charge amount decreases, the output level of the auxiliary winding nf also decreases, the polarity reverses, and bias is again applied between G and S of the FET Q1, so that the FET Q1 is turned on. After that, this is shown in FIG.
Repeat as. When the main capacitor-C2 is charged to a certain voltage or more, the circuit 3c detects the voltage of the capacitor-C3 which is almost equal to the voltage of the main capacitor-C2 by the Zener diode Z3 and detects the divided voltage of the resistors R8 and R9. Is turned on to turn off the FET Q1 between G and S, thereby stopping the oscillation of the FET Q1 and turning on the main capacitor-C2.
Hold down the voltage above a certain level. Further, an ignition timing signal is inputted from the pulser coil PC and the thyristor S1 is ignited through the gate circuit G to ignite the ignition coil 1GN. At the same time, the signal of the pulsar coil PC is input to the transistor Q2, and the transistor Q2 is made conductive, so that the FE is supplied during the same period as described above.
Stop the oscillation of TQ1. Next, DC power supply (battery)
When the voltage is low (VZ4 or less), the input voltage BAT is lower than the Zener diode Z4 and the G to S of the MOSFET Q1.
No voltage can be applied between them, and MOSFET Q1 cannot operate. Therefore, the primary current detection circuit 3a of the transformer T1
In case of low input voltage (VZ4 or less)
The operation is stopped by not applying a voltage between G and S of the OSFET Q1 and the continuity of conduction of the MOSFET is prevented.
3 (a) is the primary side (n1) current waveform of the transformer T1 (resistor R3 generated voltage), FIG. 3 (b) is the output waveform of IC1, FIG. 3 (c) is the auxiliary winding (nf) output waveform, and FIG. ) Is FE
It is an output waveform between the drain (D) and the source (s) of TQ1.

[0007]

In the prior art, the switching element was cut off when it was unsaturated, resulting in a large switching loss. However, the present invention detects the primary current of the transformer and cuts off the switching element. Switching loss is reduced. Furthermore, the switching frequency can be increased and the transformer can be downsized. Further, by making the starting circuit have a power supply voltage detecting function, it is possible to prevent the switching element from being started at a low voltage. This can be applied to the two-wheel DC-CDI.

[Brief description of drawings]

FIG. 1 Conventional circuit diagram

FIG. 2 is a circuit diagram of an embodiment of the present invention.

FIG. 3 is a waveform diagram for explaining the operation of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 converter circuit 2 capacitor charge / discharge ignition circuit (CDI) 3a primary current detection circuit 3b signal output circuit 3c secondary voltage detection circuit 3d ignition state detection circuit 3e battery voltage detection circuit Q1 field effect transistor (FET)

Claims (1)

[Claims] 1. A ringing choke type in which a switching MOS transistor is connected between a battery and a primary winding of a conversion transformer, and a rectifying diode is connected to a secondary winding side of the conversion transformer. In a capacitor charging / discharging type ignition device for charging a capacitor by the output of a converter, and discharging the charged electric charge of the capacitor to an ignition coil through a thyristor to perform ignition,
A voltage detection circuit for the battery, a circuit for detecting the primary current of the converter in proportion to the input power source, a circuit for detecting the secondary output voltage, and a detection circuit for detecting the ignition state are provided. A capacitor charging / discharging ignition device comprising a circuit for cutting the gate of the MOS transistor.