JPH03155367A - Inverter unit - Google Patents

Abstract

PURPOSE:To prevent chopper miss by controlling a chopper circuit through a minimum ON pulse circuit when PWM control is carried out based on a carrier produced on the basis of an AC input to an inverter and an output voltage from the chopper circuit. CONSTITUTION:AC carrier 12 is detected from an AC input power supply through a PT 8 and inputted to the PWM controller 9 for a drive signal generating circuit 7, an ON pulse circuit 15 and a base-up circuit 10. On the other band, a DC signal outputted from a booster chopper circuit 2 is detected 3 and an FB signal 11 is inputted to the PWM controller 9. The PWM controller 9 compares the signals 12, 11 each other to produce a pulse signal 13, and the minimum ON pulse circuit 15 forms a signal 14 in which dead time DT is removed from the carrier 12 then the signal 14 is amplified through the base-up circuit 10 and employed for control of the gate of a transistor Tr 6. By such arrangement, miss chopping of the Tr 6 due to a short pulse can be prevented resulting in a highly accurate inverter.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an inverter device that supplies DC output of a forward converter to a load via a chopper circuit.

[Prior Art] FIG. 4 is a block diagram showing a conventional inverter device. In Fig. 4, a forward converter (1) that converts AC input into DC output has a boost chopper circuit (2) and a voltage detection circuit (3) connected in parallel between its DC output terminals P and N. .

The step-up chopper circuit (2) includes a capacitor (4) connected in parallel with the forward converter (1), a transistor (6) connected in parallel with this capacitor (4) via a reactance (5), and this transistor ( 6) and a diode (29) provided in the connection path between the voltage detection circuit (3) and the collector.

A drive signal generation circuit (7) that supplies a drive signal to the base of the transistor (6) compares the detected voltage of the voltage detection circuit (3) with a carrier wave (12) from a transformer (8) that transforms the AC input. PWN controller (pulse width controller) (
9), and a base amplifier circuit (10) which receives the carrier wave (12) and the drive signal (14) voltage output from the PWM controller (9).

Next, the operation will be explained. The voltage detection circuit (3) detects the DC output voltage between the DC output terminals P and N, and based on this detected voltage, the F/B signal (11) is sent to the PWM controller (9
).

This PWM controller (9) controls the captured F/B signal (1
1) and the carrier wave (12) shown in FIG. 2 are simply compared to obtain a pulse signal (13), and from this pulse signal 13, the period (dead time) DT of the downward slope portion of the carrier wave (12) is calculated. A drive signal (14) is obtained except for.

This drive signal (14) is amplified by the base up circuit (10) and then supplied to the base of the transistor (6) to drive the transistor, operate the boost chopper (2), and convert the forward converter (1). The DC output is boosted and supplied to a load (not shown) connected to DC output terminals P and N.

[Problem to be solved by the invention] Since the conventional inverter device is configured as described above, the F/B signal (11) from the voltage detection circuit (3) and the carrier wave (12) are compared. The dead time DT is simply removed from the pulse signal (13). Therefore, when the pulse width of the drive signal (14) from the PWM controller (9) becomes extremely short, for example, as in the drive signal (14a), the drive signal generation circuit ( 7)
Despite the drive signal (14) being output from the transistor (6), the transistor (6) is not driven, resulting in an unstable operation of the boost chopper (2).

This invention has been made to solve the above-mentioned problems, and has an operation that allows the chopper circuit to operate reliably even when the pulse width of the drive signal output from the PWM controller is extremely short. The purpose is to obtain a stable inverter device.

[Means for Solving the Problems] The inverter device according to the present invention uses a drive signal to control a minimum ON pulse circuit that controls the minimum ON time of a drive signal output from a PWM controller so as to reliably operate a chopper circuit. This is included in the generating circuit.

C Effect: The minimum ON pulse circuit in this invention achieves an inverter device with high output accuracy by controlling the minimum ON time of the drive signal output from the PWM controller so as to reliably operate the chopper circuit. possible.

[Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings. In FIG. 1, in which the same parts as in FIG. 4 are given the same reference numerals,
The minimum ON pulse circuit (15) is provided on the output side of the PWM controller (9).

As shown in Fig. 2, the above minimum ON pulse circuit (15) consists of an OR gate (16) whose one input is the pulse signal from the PWM controller (9), and a resistor (17) forming a time constant circuit. and capacitor (18), or gate (
A monostable multivibrator (19) and a PWM controller (9) whose inputs are the output of 16) and the output of the time constant circuit.
) output and monostable multivibrator (1)
an EX-OR logic circuit (20) whose input is the output of the EX-OR logic circuit (20), and a comparator ( 26).

Next, the operation of the above embodiment will be explained. Forward converter (1
) converts AC input into DC output and outputs it. The boost chopper boosts the output and supplies it to the load. The voltage detection section (3) detects the output voltage of the step-up chopper, and supplies the F/B signal (11) to the PWM controller (9) based on the detected voltage. /B signal (11
) and the carrier wave (12) based on the AC input transformed by the transformer (8) to obtain the pulse signal (13), and remove the dead time DT of the carrier wave (12) from this pulse signal (13) to obtain the drive signal. (14) is output.

This drive signal (14) is input to a monostable multi-by-break (19) via an OR gate (16). This monostable multivibrator (19) is triggered at the rising edge of the drive signal (14) and outputs a pulse signal determined by a time constant circuit of a capacitor (17) and a resistor (18). This pulse signal and the drive signal (14) supplied from the PWM controller (9) through a separate path are connected to the EX-OR logic circuit (20).
Do the logic.

This shows how the short pulse width drive signal (14
), the falling edge of this drive signal (14) is detected to control the minimum ON time of the drive signal, and the drive signal after this control is shaped by a comparator (26), and then the base Output to up circuit (10).

The base amplifier circuit (10) receives the input drive signal (14).
) is amplified and supplied to the base of the transistor (6) to make the transistor conductive, thereby operating the boost chopper circuit (2) and boosting the DC output output from the forward converter (1). So, this bass amplifier circuit (1
0) is the same as the conventional example shown in FIG. 4.

In addition, in the above embodiment, the minimum ON time that controls the minimum ON time of the drive signal to reliably operate the boost chopper circuit is
Although the pulse circuit (15) has been described, it may be a minimum ON pulse circuit of a step-down chopper circuit.

Furthermore, in the above embodiment, the minimum ON pulse circuit (15) was constructed using a monostable multivibrator, but as shown in FIG. 5, in which the same parts as in FIG. 2 are given the same reference numerals, Even if the filter circuit (27) is configured in combination with a comparator (28) having hysteresis characteristics, the same effects as in the above embodiment can be obtained.

[Effects of the Invention] As described above, according to the present invention, since the drive signal is configured to be controlled to a pulse width that reliably operates the chopper circuit, there is an effect that an inverter device with high output accuracy can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an inverter device according to an embodiment of the present invention, FIG. 2 is a circuit diagram showing a minimum ON pulse circuit, FIG. 3 is a circuit diagram showing another example of the minimum ON pulse circuit, and FIG. FIG. 4 is a block diagram of a conventional inverter device, and FIG. 5 is a signal waveform diagram illustrating the operation of a PWM controller. In the figure, (1) is a forward converter, (2) is a boost chopper circuit, (3) is a voltage detection circuit, (9) is a PWM controller,
(15) is a minimum ON pulse circuit. Note that the same reference numerals in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of Claims] A forward converter that converts an AC input into a DC output, a chopper circuit that intermittents the DC output, a voltage detection circuit that detects the output voltage of the chopper circuit, and a detection voltage of the voltage detection circuit. and a carrier wave based on the AC input to output a drive signal.
Minimum ON that controls the minimum ON time of the controller and the drive signal
An inverter device comprising a drive signal generation circuit having a pulse circuit.