JPH0638513A - High power factor power circuit - Google Patents

Abstract

PURPOSE:To make a stable drive signal with a digital circuit by lessening parts for adjustment in case of making a power circuit which materializes high power factor, using a chopper circuit. CONSTITUTION:This is one which materializes high power factor, making use of the ripple of input voltage, and making use of a current flowing with timing suited to it, and in this case, it can be materialized by making a drive pulse of fixed frequency. This is constituted of a digital circuit. As the content of constitution, drive frequency is constituted of an 8-bit counter (a) and a comparator (b), and drive pulses are made by changing the duty ratio with a comparator (c). In addition to this, feedback control becomes necessary fix power source output voltage. As to this, there is as up/down counter circuit (d) which makes the reference number of counts of the comparator (c).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a high power factor power supply circuit,
In particular, it relates to a power source in an inverter circuit for lighting.

[0002]

2. Description of the Related Art A conventional high power factor power supply uses a dedicated analog IC. Siemens TD is the representative IC
There is A4814, and its concrete circuit configuration is shown in FIGS.
Shown in. Incidentally, FIG. 5 shows a chopper circuit, and FIG. 6 shows a control circuit thereof. In the figure, the output voltage 1 of the full-wave rectifier DI,
A current 2 flowing through the primary side of the step-up transformer ST, a current 3 flowing through the field effect transistor Q, and a secondary voltage 4 serving as a DC output are detected, and a gate drive signal 5 for the transistor Q is generated from the detected state.

Next, the operation will be described. First, the difference is taken by the control amplifier 6 using the secondary voltage 4 and the output reference voltage, and the multiplier 7 produces a product of the difference and the voltage waveform of the output voltage 1 of the full-wave rectifier DI. This is a voltage that is proportional to the input voltage value at a certain moment, and the transistor Q is turned on until it matches. Whether or not they match is determined by the comparator 8 based on the output voltage (3) of the transistor Q and the output of the multiplier 7. If it is judged to be correct Transistor Q
Is turned off and continues to be turned off until the current flowing through the boosting transformer ST becomes zero, and when it becomes zero, the transistor Q is turned on again. By repeating the above, the current flows through the transformer ST with a current waveform as shown in FIG. Looking at this for only one half cycle of the voltage waveform, it becomes as shown in FIG. By smoothing this Nocogill wave with the input noise filter NF, a current waveform of SIN wave synchronized with the input voltage as shown by 11 at 8 is obtained. In this method, the frequency changes according to the input voltage, and the noise filter NF having a wide frequency is required. In order to increase the power factor, the circuit is complicated in that the ON time of the switching element is controlled by detecting the input voltage or the current flowing in the choke of the chopper type booster circuit. In addition, since the drive pulse is generated in analog, it was difficult to determine the constant of each component.

[0004]

In the conventional method, since all the control is performed by analog, many adjusting parts are required. In addition, since it does not oscillate at a constant frequency, there is a problem that a proper filter is required.

Therefore, an object of the present invention is to process a main drive waveform digitally, to reduce the number of adjusting parts as much as possible, and to oscillate at a constant frequency, thereby making it possible to provide a power supply which is easy to control and has low noise. Is to provide.

[0006]

Therefore, in order to achieve the above-mentioned object, the present invention provides a step-up chopper circuit for driving a switching element at a constant frequency and a drive pulse for driving the switching element at a constant frequency. A drive pulse generation circuit for producing the drive pulse generation circuit is used.The drive pulse generation circuit is a digital circuit and is composed of a counter, a comparator, a decoder, and a comparator as an input to the digital section. is there.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, one embodiment of the present invention will be described with reference to FIGS.
Will be described with reference to.

FIG. 1 is a basic circuit using a chopper type booster circuit. A filter e, a full-wave rectifier (diode bridge) f, a choke coil g, and a diode i are connected between an AC power source and a load K. ing. A switching element such as a field effect transistor h is connected between the output side lines of the choke coil g. A series circuit of a capacitor j and a resistor is connected in parallel to the load K. The drive pulse generated by the drive pulse generation circuit shown in FIG. 2 is applied to the gate of the transistor h. This drive pulse generating circuit is composed of a digital circuit. The basic circuit consists of an 8-bit counter a, comparators b and c, an up / down counter d, etc. The basic operation is to count the 8-bit counter a from 0 at a constant speed, and that value is a unique set value (corresponding to the frequency). ) Is counted by comparator b
Then, the counter a is reset at the time when the count reaches the set value, and the count is restarted from 0. The main frequency is created by repeating this. For the drive pulse to the transistor h, one cycle is from the time the main counter a is 0 until the reset is applied
It is realized by dividing it into ON and OFF times. This is a method of dividing into ON and OFF times, but this uses the comparator C. This duty ratio, which varies with the two-dimensional voltage, is feedback controlled.

According to the present invention, by driving the drive pulse at a constant frequency as shown in FIG. 3, a current proportional to the input voltage flows and a high power factor is realized. Regarding stabilization of the secondary voltage, the capacitor j of FIG.
The voltage across both ends of the
The input voltage to MP is compared with the reference voltage, and while the drive frequency is constant, only the ON time (duty ratio) is changed to perform feedback control to stabilize the secondary voltage.

[0010]

According to the present invention, the power factor can be increased with a simpler circuit as compared with the conventional method, and the power factor can be increased without requiring difficult detection. As for feedback, it can be realized by a simple one that uses a comparator because it only changes the pulse width.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram showing an embodiment of the present invention.

FIG. 2 is a block diagram of a drive pulse generation circuit according to the present invention.

FIG. 3 is a waveform diagram of a drive pulse.

FIG. 4 is a feedback circuit diagram including a drive pulse generation circuit.

FIG. 5 is an electric circuit diagram showing a conventional example.

FIG. 6 is a control circuit diagram of FIG.

FIG. 7 is a waveform diagram of a current flowing through a transformer.

FIG. 8 is a waveform diagram on the output side of the noise filter.

[Explanation of symbols]

 a 8-bit counter b, c comparator d up / down counter e filter f full-wave rectifier h switching element k load

Claims (2)

[Claims] 1. A high power factor comprising a booster chopper circuit for driving a switching element at a constant frequency and a drive pulse generating circuit for generating a drive pulse for driving a switching element at a constant frequency. Power supply circuit. 2. The high power factor power supply circuit according to claim 1, wherein the drive pulse generating circuit is composed of a counter, a comparator, a decoder and a comparator using a digital circuit.