JPH01186167A - Power unit - Google Patents

Abstract

PURPOSE:To remove waveform distortion, by providing a second rectification means separate from and independent of a first rectification means so as not to be affected by the discharging current of the first capacitor. CONSTITUTION:A power unit is composed of an FET 3, a bridge rectifier D1, a low-pass filter LPF, capacitors C1-C2, a choke coil L1, a diode D2. a control amplifier 4, a multiplier 5, a comparator 6 and a gate control circuit 7. Another bridge rectifier D3 is connected so as to be in parallel to the rectifier D 1 to input terminals 1A-1B, of which the output voltage V 3 is resistively divided to input into the multiplier 5. No waveform of the output voltage V3 of the rectifier D3 will be affected by the capacitor C1 connected to the output terminal of the rectifier D1. Distortionless output can thereby be obtained at an output terminal 2.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a power supply device.

[Prior Art] An active smoothing filter in a power supply device is designed to prevent noise caused by sudden current changes from being generated on the primary side by making the rectified current waveform similar to the voltage waveform. be.

FIG. 2 shows a conventional power supply device using an active smoothing filter. This power supply device basically consists of a DC-DC converter (step-up type) applied to a smoothing circuit. As shown in Figure 2, a power supply with a rated voltage of commercial frequency is connected to the input terminals IA and IB, and a bridge rectifier D1 is connected to the input terminal via a low-pass filter LPF.
A rectified output v1 is obtained at the + (plus) output terminal of. A choke coil L is installed at the output end of the rectifier (diode) Dl.
The anode of a diode (flywheel diode) D2 is connected to the other end of the coil L1, and the cathode of the diode D2 is connected to the output terminal 2. C2 is a capacitor connected to the cathode of the diode 02.

Resistors R1 and R2 connected in series are connected between the output terminal of the rectifier O1 and ground, and a capacitor CI is also connected. A series circuit of a FET (field effect transistor) 3 (its source and drain) and a resistor R3 is connected between the other end of the choke coil L1 and the ground. A detection winding L2 for current detection is wound around the choke coil Ll. The output end voltage of the detection winding L2 is at a high (H) level while the choke coil Ll is discharging the stored energy.

Reference numeral 4 denotes a control amplifier consisting of a differential amplifier, the reference voltage is input to the non-inverting input terminal, the voltage of the output terminal 2 (output of the diode D2) is input to the inverting input terminal, and the target value is input to the output terminal. A direct current (OC) output is obtained for determining the magnitude of . 5 is a multiplier, and one input terminal receives the output of the control amplifier 4, and the other input terminal receives a voltage obtained by dividing the rectified output Vl by resistors R1 and R2, respectively. and obtain the threshold value (target value) as the output.

6 is a comparator consisting of a differential amplifier, and the output of the multiplier 5 is input to the non-inverting input terminal, and the voltage of the shunt resistor R3 is input to the inverting input terminal.

The voltage drop detected by the shunt resistor R3 when the FET3 is conductive corresponds to the instantaneous value of the current flowing through the coil Ll.

The output of the comparator 6 is the voltage value of the shunt resistor R3.
Turns off (Low) when the output value (i.e. target value) is reached.
become. Reference numeral 7 denotes a gate control circuit which manually inputs the output of the comparator 6 and turns off the gate of the FET 3 when the output is turned off. Then, the gate control circuit 7 turns on the gate of the FET 3 when the choke coil LL finishes discharging and the output terminal voltage of the detection winding L2 becomes zero.

According to the above configuration, during the conduction period of FET3, the choke coil L1 flows current while accumulating magnetic energy, and when this current reaches a peak value (target value), FET3
is turned off, coil L1 starts discharging while passing current, and at the end of discharging, the output terminal voltage of detection winding L2 becomes zero, FET3 is turned off, and choke coil L
l begins to flow current while accumulating magnetic energy again. By operating in this manner, the average value current i of the current iL flowing through the choke coil Ll can be changed in accordance with the waveform of the voltage Vl that changes at the commercial frequency, as shown in the third column (3). Since the current flowing through the choke coil Ll has a relatively high frequency, its influence is removed by the low-pass filter LPF, and noise etc. do not leak to the primary side.

[Problems to be Solved by the Invention] However, in the above power supply device, since the capacitor CI is provided between the bridge rectifier DI and the choke coil Ll, as shown in the third section (3), the output voltage Vl of the rectifier DI is The charge charged in the capacitor CI at the peak portion vp enters the next voltage rise without being completely discharged. As a result, the capacitor CI has a voltage vl due to the residual charge at the zero cross (t2) for the commercial power supply voltage. remains, and this voltage v1 also influences the voltage v2 taken out between the resistors R1 and 82. Therefore, since this voltage v2 is input to the multiplier 5, its adverse effect also extends to the input terminal II of the rectifier DI, resulting in noise leakage.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a power supply device that does not leak noise.

[Means for Solving the Problems] The present invention provides a first rectifier that rectifies an AC signal from an AC power source, a choke coil that connects an output end of the rectifier to a smoothing output end, and a first rectifier that connects an input end of the choke coil to a ground. connect between
741 capacitor, a second capacitor that connects the output end of the choke coil and the ground, a switch that turns on/off the continuity between the output end of the choke coil and the ground, and rectifies the AC signal from the AC power supply in the same phase as the first rectifier. and means for controlling the switch on/off based on the rectified output signal from the second combing means and the signal flowing to the switch.

[Function] According to the present invention, the first rectifier and the independent second rectifier or the reverse blocking diode are used to prevent the influence of the discharge current from the first capacitor, and to control the on/off of the switch. Get information about. This eliminates the occurrence of so-called waveform distortion and prevents noise from leaking to the primary side.

[Example] Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of the present invention.
The same parts as in the figure are given the same reference numerals.

That is, IA and IB are input terminals, 2 is output terminal, 3 is FET, Di is bridge rectifier, LPF is low pass filter, CI and C2 are capacitors, Ll is choke coil, Ll is detection winding, and D2 is diode. . 4 is a control amplifier, 5 is a multiplier, 6 is a comparator, and 7 is a gate control circuit. The feature of this embodiment is that the input terminal IA
, IB connects another bridge rectifier D3 in parallel with the rectifier DI (via the LPF), and this rectifier D3
The reason is that the voltage v2 obtained by dividing the output voltage v3 of the output voltage v3 by the resistors R1 and R2 is inputted to the multiplier 5.

According to this configuration, the waveform of the output voltage v3 of the rectifier D3 is not affected by the capacitor CI connected to the output terminal of the rectifier DI, that is, it becomes a distortion-free waveform as shown in Figure 2 (■). . Therefore, by manually inputting the voltage v2 obtained by dividing the voltage v3 to the multiplier 5,
A distortion-free output can be obtained at the output terminal 2, and as a result, no noise appears on the input terminals IA and IB.

FIG. 4 shows another embodiment of the invention. This embodiment is characterized in that a charging current is applied to the capacitor CI via the diode D4, and the other configurations are exactly the same as that of FIG. 2. According to such a configuration, since the discharge current of the capacitor C1 is blocked by the diode D4,
It does not affect the voltage v2, so a distortion-free output is obtained at the output terminal 2, and no noise appears on the primary side.

[Effects of the Invention] As described above, according to the present invention, it is possible to obtain a power supply device that does not leak noise to the primary side.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing one embodiment of the present invention, Fig. 2 is a circuit diagram of a conventional power supply device, Fig. 3 is a diagram showing a rectifier output waveform, and Fig. 4 is a diagram showing another embodiment of the present invention. It is a circuit diagram.

Claims (1)

[Claims] 1) A first rectifier for rectifying an AC signal from an AC power source; a choke coil connecting the output end of the rectifier to a smoothing output end; and a connection between the input end of the choke coil and ground. a first capacitor that connects the choke coil to the ground; a second capacitor that connects the output end of the choke coil to the ground; a switch that turns on/off continuity between the output end of the choke coil and the ground; and a switch that connects the AC signal from the AC power source to the first A power source comprising: a second rectifier that rectifies in the same phase as the rectifier; and a means for controlling the switch on and off based on a rectified output signal from the second rectifier and a signal flowing to the switch. Device. 2) rectifying means for rectifying an alternating current signal from an alternating current power source; a diode having an anode connected to the output end of the rectifying means; a choke coil connecting the cathode of the diode to a smooth output end; and an input end of the choke coil. a first capacitor that connects between the output end of the choke coil and the ground; a second capacitor that connects the output end of the choke coil with the ground; a switch that turns on/off continuity between the output end of the choke coil and the ground; and a switch that connects the output end of the choke coil with the ground. A power supply device comprising means for controlling on/off of the switch based on a rectified output signal of the switch and a signal flowing through the switch.