JPH10312221A - Power source device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source device reducing noise leakage to an AC power source. SOLUTION: A switch circuit 100 and a lamp HL1 are serially connected to the input terminals 1 and 2 of the AC power source through noise filters L1 and C1. To the switch circuit 100, electric field effective transistors Q111 and Q121 are serially connected in the form of directly connecting their source terminals with each other to supply a pulse width modulating signal of a frequency sufficiently higher than the frequency of the AC power source between a source and a gate. Thus, the circuit 100 is turned on/off by a frequency sufficiently higher than the frequency of an inputted AC power source and noise generated at the time is sufficiently blocked by a noise filter and is never leaked to the side of the AC power source.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device suitable for a lamp regulator for stably turning on a light source lamp such as a halogen lamp used for reading an original of a copying machine.

[0002]

2. Description of the Related Art Conventionally, as a lamp regulator for a copying machine, a method has been used in which an AC input is phase-controlled by an AC control element such as a triac to stabilize a voltage and supply the voltage to a lamp.

FIG. 6 shows a configuration of a conventional lamp regulator. 6, input terminals 1 and 2 are connected to a waveform shaping circuit 700 via a noise filter circuit composed of a choke coil L1 and a capacitor C1, and one input terminal 1 is connected via a noise filter circuit. The triac Q1 is connected to one input / output terminal, the other input terminal 2 is connected via a noise filter circuit to one terminal of a lamp HL1 serving as a load, and the other input / output terminal of the triac is connected to the lamp HL1. Is connected to the other terminal. In the gate terminal of Triac Q1,
The output terminal of the trigger circuit 800 is connected.

In order to detect the terminal voltage of the lamp HL1 serving as a load, input terminals 201 and 202 of a level conversion circuit 200 are connected to both ends of the lamp HL1.

The output terminal 203 of the level conversion circuit 200
Is connected to the input terminal 301 of the comparison circuit 300, and the reference voltage terminal 302 of the comparison circuit 300 is connected to a reference voltage source for setting the output voltage. In this embodiment, a predetermined voltage is obtained by dividing a voltage source for a control circuit (hereinafter referred to as VCC) by a variable resistor VR1 as a reference voltage source.

An output terminal 303 of the comparison circuit 300 is connected to an input terminal 801 of the trigger circuit 800. The input terminal 802 of the trigger circuit 800 is connected to the output terminal 703 of the waveform shaping circuit 700, and the output terminals 803 and 804 are connected to the gate terminal of the triac Q1.

Next, the operation of each circuit in FIG. 6 will be described.

A commercial AC power supply is connected to the input terminals 1 and 2. Choke coil L connected to input terminals 1 and 2
The noise filter circuit including the capacitor C1 prevents the noise generated by the next-stage triac Q1 from leaking to the commercial power supply.

[0009] The triac Q1 switches and controls the load HL1 inserted in series with the circuit. It is controlled by a trigger circuit 800 connected to the gate terminal. It is turned on by a trigger signal and turned off at zero cross.

The level conversion circuit 200 includes an insulating transformer T
201, rectifying elements D201-204, resistors R201-2
07, a capacitor C201 and an operational amplifier Q201, a voltage signal applied between the input terminals 201 and 202 is converted to a predetermined voltage level by an insulating transformer T201, and then full-wave rectified by diodes D201 to D204.
The rectified pulsating signal is converted into a DC signal by a filter circuit including resistors R201 and R202 and a capacitor C201. The signal converted to DC is connected to a resistor R203.
207 and an operational amplifier Q201, the signal voltage level and the offset voltage level are converted to predetermined values, and the converted detection voltage signals are output to the comparison circuit 300.

The comparison circuit 300 includes an operational amplifier Q301,
The level conversion circuit 2 includes resistors R301 and R302.
00 and the reference voltage terminal 302
, And outputs an error voltage signal to the trigger circuit 800 as an output signal.

The waveform shaping circuit 700 shapes the waveform of the input commercial sine wave alternating current, generates a sawtooth wave of the commercial frequency, and outputs the sawtooth wave to the trigger circuit 800.

The trigger circuit 800 compares the error voltage signal output from the comparison circuit 300 with the sawtooth wave output from the waveform shaping circuit 700 to determine a trigger phase.
Trigger output via trigger transformer TRIAC Q1
Output to In the triac Q1, switching control for turning on at a phase angle corresponding to a target voltage is performed by a trigger signal applied from the trigger circuit 800.

As described above, by detecting the load voltage and controlling the trigger phase of the triac Q1, the load voltage is stabilized.

[0015]

However, in the above-mentioned conventional example, since the constant voltage control is performed by the phase control, there is a problem that the input current contains many low-order harmonics of the commercial frequency. Since the low-order harmonics are noise having a low frequency close to the commercial frequency, it is difficult to remove them with an LC filter or the like, and the noise leaks to the commercial power supply system, causing a problem to peripheral equipment.

The present invention has been made under such a situation, and an object of the present invention is to provide a power supply device with less noise leakage to an input AC power supply side.

[0017]

In order to achieve the above-mentioned object, according to the present invention, a power supply is provided by the following (1), (2),
The configuration is as shown in (3).

(1) A power supply device in which a switch circuit and a load terminal are connected in series to an input terminal of an AC power supply via a noise filter circuit, wherein the switch circuit includes an even number of field effect transistors connected to a source terminal. They are connected in series so that they are directly connected to each other, and the drain terminal at the end is used as the input terminal and the output terminal of the switch circuit, and the frequency of the AC power supply is connected between each gate terminal and the source terminal which is a common connection point. A power supply device for applying a drive signal having a sufficiently larger frequency.

(2) The AC power supply is a commercial AC power supply, the load is a lamp, and the drive signal is a pulse width modulation signal based on an error voltage obtained by comparing the lamp voltage with a reference voltage. The power supply as described.

(3) The power supply according to (2), wherein the reference voltage is generated by comparing the lamp voltage with a target value and performing an arithmetic processing.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to examples of a lemp regulator.

[0022]

【Example】

(Embodiment 1) FIG. 1 is a circuit diagram showing a configuration of a "lamp regulator" which is Embodiment 1. In FIG. 1, a commercial AC power supply is connected to input terminals 1 and 2.

One input terminal 1 is connected to a choke coil L
1, connected to the input terminal 101 of the switch circuit 100 via a noise filter circuit composed of a capacitor C1. The other input terminal 2 is connected to one terminal of a lamp HL1 serving as a load via a noise filter circuit. The output terminal 102 of the switch element is connected to the other terminal of the lamp.

In order to detect the terminal voltage of the lamp HL1 serving as a load, input terminals 201 and 202 of the level conversion circuit 200 are connected to both ends of the lamp HL1.

Output terminal 203 of level conversion circuit 200
Is connected to the input terminal 301 of the comparison circuit 300, and the reference voltage terminal 302 of the comparison circuit 300 is connected to a reference voltage source for setting the output voltage. In this embodiment, a predetermined voltage is obtained by dividing the voltage of the control circuit voltage source (hereinafter referred to as VCC) by the variable resistor VR1.

The output terminal 303 of the comparison circuit 300 is connected to the input terminal 40 of a pulse width modulation circuit (hereinafter referred to as a PWM circuit).
1, the input terminal 402 of the PWM circuit 400 is connected to the output terminal 603 of the oscillation circuit 600.

The output terminal 403 of the PWM circuit 400 is connected to the input terminal 501 of the drive circuit 500.

Output terminals 503 and 504 of drive circuit 500
Are connected to the drive terminals 104 and 105 of the switch circuit 100.

Next, the operation of each circuit in FIG. 1 will be described.
A commercial AC power supply is connected to the input terminals 1 and 2. The filter circuit including the choke coil L1 and the capacitor C1 prevents high-frequency noise generated by the next-stage switch circuit 100 from leaking to the commercial power supply.

The switch circuit 100 includes two field effect transistors Q111 and Q121 and a gate driving resistor R1.
11, 112, 121, and 122. The drain terminal of one field effect transistor Q111 is the input terminal 101, and the drain terminal of the other field effect transistor Q121 is the output terminal 102. The field effect transistors Q111 and Q121 connect their sources to each other to form the drive circuit 104, and each gate terminal is connected to the drive terminal 1 via a resistor.
05. The drive signals are supplied to the drive terminals 104 and 10
5 is applied. A plurality of devices are connected in parallel to the field effect transistors Q111 and Q121 as needed.

The level conversion circuit 200 includes an insulating transformer T2
01, rectifiers D201-204, resistors R201-20
7, a detection voltage signal which is composed of a capacitor C201 and an operational amplifier Q201, insulates the signal voltage applied to the transformer T201 and converts the signal voltage to a voltage of a predetermined signal level is output from an output terminal 203.

The comparison circuit 300 includes an operational amplifier Q301,
It is composed of resistors R301 and R302, compares the voltage of the input terminal 301 with the terminal voltage of the reference voltage terminal 302, and outputs an error voltage signal from the output terminal 303.

The PWM circuit 400 includes a comparator Q40
At 1, the error voltage signal applied to the input terminal 401 is compared with the sawtooth wave applied to the input terminal 402, and the PWM
A modulated high-frequency signal is generated and output from an output terminal.

The drive circuit 500 includes an amplifier Q501 and a drive transformer T501. The drive circuit 500 amplifies a high-frequency signal input to the input terminal 501, insulates the drive signal with the drive transformer T501, and outputs the output signals from the output terminals 503 and 504.

The oscillation circuit 600 generates a sawtooth wave having a frequency sufficiently higher than the commercial frequency, and outputs the sawtooth wave from the output terminal 603.

Next, the operation in a state where a commercial AC power supply is connected to the input terminals 1 and 2 and the load lamp HL1 is controlled at a constant voltage will be described. FIGS. 2 and 3 show waveforms of respective parts in the constant voltage control state.

11 is a terminal voltage between the input terminals 1 and 2;
Is a terminal voltage of the lamp HL1 serving as a load, and 13 is a terminal voltage of a drive signal applied between the drive terminals 104 and 105 of the switch circuit.

The switch circuit 100 includes a driving terminal 104,
The drive signal 13 is applied to 105 to perform on / off control.

The field effect transistors Q111 and Q121, which are switch elements of the switch circuit 100, are turned on and off simultaneously according to a drive signal applied between the drive terminals 104 and 105.

During the period in which the drive signal corresponding to the ON state is applied, the field effect transistors Q111 and Q121 are bidirectional elements that conduct in either direction from the drain to the source or from the source to the drain. During the period in which the drive signal corresponding to the OFF state is applied, the direction of the current is non-conductive from the drain to the source, and the current flows from the source to the drain by a parasitic element.

In the switch circuit 100, two field-effect transistors are connected in series in the reverse direction. Therefore, the switch circuit 100 has an element that conducts bidirectionally during a period in which a drive signal corresponding to ON is applied. In the period in which the drive signal corresponding to the OFF state is applied, the signal is equivalent to the non-conductive element in both directions.

The number of the field effect transistors is not limited to two, but may be an appropriate even number in series according to the power supply voltage. At this time, a plurality of secondary windings are provided in the drive transformer T501, and each is connected in the same manner as shown. Also, a plurality of field effect transistors can be connected in parallel according to the output current.

By using a pulse width modulation signal generated by a control loop described below as the drive signal, the lamp voltage can be controlled by pulse width modulation.

To perform constant voltage control, the input terminals 201 and 20 of the level conversion circuit 200 are connected between the terminals of the lamp HL1.
2 is connected to detect the terminal voltage of the lamp HL1.

The input terminals 201,
The voltage signal applied between the two is connected to an isolation transformer T201.
After converting to a predetermined voltage level, the diode D201
Full-wave rectification is performed at 204. The rectified pulsating signal is a resistor R2
The signal is converted into a DC signal by a filter circuit composed of the C.01, 202 and the capacitor C201. The DC converted signal is supplied to the resistors R203 to R207 and the operational amplifier Q2.
The signal level converter circuit 01 converts the voltage level and the offset level to predetermined values, and outputs the detected voltage signal 21 converted to the predetermined values to the comparison circuit 300.

The winding specification of the insulating transformer T201 is appropriately determined according to the lamp voltage, the corresponding standard, and the like. The level of the detection voltage signal 21 is set to an appropriate value according to the dynamic range of the comparison circuit 300 and the value of the reference voltage 22.

The detection voltage signal 21 input to the input terminal 301 of the comparison circuit 300 is compared with the reference voltage signal 22 applied to the reference voltage terminal 302, and outputs an error voltage signal 23 generated to the PWM circuit 400.

A predetermined voltage corresponding to a desired lamp voltage is applied to the reference voltage signal.

The PWM circuit 400 performs pulse width modulation of the error voltage signal 23 applied to the input terminal 401 with the sawtooth wave 24, and outputs a pulse width modulated digital signal (hereinafter referred to as a PWM signal) 24 to the drive circuit 500. I do.

The pulse width of the PWM signal 25 changes according to the value of the error voltage signal 23. As shown in FIG. 3, as the value of the error voltage signal 23 increases, the pulse width decreases, and as the value of the error voltage signal 23 decreases, the pulse width increases.

The drive circuit 500 drives the drive transformer T501 after amplifying the PWM signal to a level at which the drive transformer T501 can be driven. The drive transformer T501 is
Provides signal isolation and voltage level conversion. Drive transformer T
The drive signal 13 as a secondary output of 501 becomes a signal of a level capable of driving the field effect transistors Q111 and Q121 as shown in FIGS. The winding specification of the drive transformer T501 is appropriately determined according to the value of VCC, the corresponding standard, and the like.

The drive signal 13 is applied to drive terminals 104 and 105 of the switch circuit 100,
Is subjected to PWM control. As a result, the lamp terminal voltage is controlled at a constant voltage.

As described above, according to this embodiment, the switch circuit controls the switching of the commercial power at a frequency sufficiently higher than the frequency of the commercial power by the control loop for detecting the load voltage and performing the PWM control. By stabilizing the voltage, the frequency of the generated noise is only a frequency component that is sufficiently higher than the frequency of the commercial power supply, and the noise can be sufficiently removed with a small noise filter, and the lamp with little leakage noise to the commercial power supply system A regulator can be realized.

(Embodiment 2) FIG. 4 is a circuit diagram showing a configuration of Embodiment 2. In FIG. 4, a commercial AC power supply is connected to input terminals 1 and 2.

One input terminal 1 is connected to a choke coil L
1, connected to the input terminal 101 of the switch circuit 100 via a noise filter circuit composed of a capacitor C1. The other input terminal 2 is connected to one terminal of a lamp HL1 serving as a load via a noise filter. The output terminal 103 of the switch circuit 100 is connected to the other terminal of the lamp.

To detect the terminal voltage of the lamp HL1 serving as a load, input terminals 201 and 202 of the level conversion circuit 200 are connected to both ends of the lamp HL1.

Output terminal 203 of level conversion circuit 200
Is connected to the input terminal 301 of the comparison circuit 300 and to the analog input port 901 of the CPU 900. The analog input port is a port that converts an analog level into a numerical value and reads it into the CPU 900. In a small-scale CPU, an A / D conversion circuit is added to a digital input port to be an analog input port.

The reference voltage terminal 302 of the comparison circuit 300 serves as a reference voltage source for setting an output voltage.
00 analog output port 903 is connected. The analog output port 903 is a port for converting the numerical value of the operation result of the CPU 900 into an analog level and outputting the analog level. In a small-scale CPU, the digital output port is connected to the digital output port.
A conversion circuit is added to make an analog output port.

The output terminal 303 of the comparison circuit 300 is connected to the input terminal 401 of the pulse width modulation circuit, and the input terminal 402 of the PWM circuit 400 is connected to the output terminal 603 of the oscillation circuit 600.

The output terminal 403 of the PWM circuit 400 is connected to the input terminal 501 of the drive circuit 500. The output terminals 503 and 504 of the drive circuit 500 are connected to the switch circuit 100
Drive terminals 104 and 105.

Next, the operation of this embodiment will be described. In addition,
The switch circuit 100, the level conversion circuit 200, the comparison circuit 300, the PWM circuit 400, the drive circuit 500, and the oscillation circuit 600 are the same as those in the first embodiment, and the description of the operation of each circuit is omitted.

A commercial AC power supply is connected to the input terminals 1 and 2. The filter circuit including the choke coil L1 and the capacitor C1 prevents high-frequency noise generated by the next-stage switch circuit 100 from leaking to the commercial power supply.

The CPU 900 is an integrated circuit having a power supply control function, and incorporates a program for controlling the voltage applied to the analog input port 901 at a constant voltage.
Input port 901 to the voltage value determined by the program
The output value is PWM controlled so as to maintain the voltage of The PWM signal is output from the analog output port 903 as a D / A converted DC voltage value.

Next, the operation in a state where a commercial AC power supply is connected to the input terminals 1 and 2 and the load lamp HL1 is controlled at a constant voltage will be described. Since the waveforms of the respective parts in the constant voltage control state are the same as those in the first embodiment, description will be given with reference to FIGS.

Reference numeral 11 denotes a voltage between input terminals, 12 denotes a terminal voltage of the lamp HL1 serving as a load, and 13 denotes a terminal voltage of a drive signal applied between the drive terminals 104 and 105 of the switch circuit 100.

The detected voltage signal 21 input to the input terminal 301 of the comparison circuit 300 is compared with the reference voltage signal 22 applied to the reference voltage terminal 302, and outputs an error voltage signal 23 generated to the PWM circuit 400. Reference voltage signal 2
2, a voltage signal generated by a CPU 900 described later is applied. The relationship among the drive signal 13, the reference voltage signal 22, and the error voltage signal 23 is the same as in the first embodiment. Drive signal 13, error voltage signal 23, sawtooth wave 24, PWM signal 2
The relationship of 5 is the same as that of the first embodiment.

The pulse width of the PWM signal 25 changes according to the value of the error voltage signal 23. As the value of the error voltage signal 23 increases, the pulse width decreases, and as the value of the error voltage signal 23 decreases, the pulse width increases.

The drive signal 13 is applied to drive terminals 104 and 105 of the switch circuit 100,
Is subjected to PWM control. As a result, the lamp terminal voltage is controlled at a constant voltage according to the reference voltage signal 22.

In order to control the reference voltage signal 22, the CPU 900 reads the value of the detected voltage signal 21 from the analog input port 901, performs a comparison operation with a programmed desired voltage, and outputs a control value. The output control value is converted to an analog level, and the analog output port 9
03 is applied to the comparison circuit 300 as the reference voltage signal 22.

The constant voltage control processing routine of the CPU 900 will be described. The constant voltage control processing routine is executed at predetermined intervals by a timer interrupt or the like. VSET is a reference voltage value corresponding to a desired output voltage target value specified by the main program. When the target value is changed, it is updated by the main program. α is a hysteresis width in the constant voltage control. β is a control step in constant voltage control.

The constant voltage control processing routine will be described with reference to FIG. First, in step 10, an input value V1 corresponding to the analog value 21 corresponding to the load voltage is determined. In step 11, it is determined whether or not the input value V1 is lower than a value obtained by adding the hysteresis α to the reference voltage value VSET. If NO, the control step value β is subtracted from the reference voltage value VSET in step 12, and in step 13, The reference voltage value VSET is set to D /
After the conversion into the analog output value 22 by the A conversion, the process returns to the main routine. In the case of YES in step 11, the process proceeds to step 14. In step 14, it is determined whether or not the input value V1 is higher than a value obtained by subtracting the hysteresis α from the reference voltage value VSET.
The control step value β is added to SET, and in step 16 the reference voltage value VSET is converted into an analog output value 2 by D / A conversion.
After the conversion to 2, the program returns to the main routine. Step 14
If the answer is YES, the process returns to the main routine.

The control loop characteristic is that the first control loop for controlling the lamp voltage based on the reference voltage has a response speed as a constant capable of high-speed response, and controls the reference voltage signal 22 by a program. The second loop is a high-precision control loop in which accuracy is prioritized, whereby high-precision control with high response speed, which is difficult when performed by a single normal control loop, becomes possible.

As described above, according to the present embodiment, by providing a plurality of control loops for detecting a load voltage and performing PWM control, control characteristics with high accuracy and good responsiveness can be obtained.
The switch circuit is at a frequency sufficiently higher than the commercial power supply frequency.By controlling the switching of the commercial power supply and stabilizing the load voltage, the frequency of the generated noise is only a frequency component sufficiently higher than the commercial power supply frequency. Noise can be sufficiently removed with a small noise filter, and a lamp regulator with little noise leakage to the commercial power supply system can be realized.

[0074]

As described above, according to the present invention,
A power supply device with less noise leakage to the input AC power supply can be provided. According to the third aspect of the present invention,
Furthermore, a high-speed stabilization control with a high response speed can be obtained.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a first embodiment.

FIG. 2 is a waveform diagram of each part.

FIG. 3 is a waveform diagram of each part.

FIG. 4 is a circuit diagram of a second embodiment.

FIG. 5 is a flowchart of a constant voltage control processing routine.

FIG. 6 is a circuit diagram of a conventional example.

[Explanation of symbols]

 1, 2 input terminal 100 switch circuit C1 capacitor HL1 lamp L1 choke coil Q111, Q121 field effect transistor

Claims (3)

[Claims] 1. A power supply device in which a switch circuit and a load terminal are connected in series to an input terminal of an AC power supply via a noise filter circuit, wherein the switch circuit connects an even number of field effect transistors to source terminals. Are connected directly in series such that the drain terminal at the end is an input terminal and an output terminal of the switch circuit, and is connected between each gate terminal and a source terminal, which is a common connection point, based on the frequency of the AC power supply. A power supply device for applying a drive signal having a sufficiently large frequency. 2. The AC power supply is a commercial AC power supply, the load is a lamp, and the drive signal is a pulse width modulation signal based on an error voltage obtained by comparing the lamp voltage with a reference voltage. The power supply device according to claim 1. 3. The power supply device according to claim 2, wherein the reference voltage is generated by comparing the lamp voltage with a target value and performing arithmetic processing.