TWI436587B - Bleeding circuit and method for power reduction of an emi filter - Google Patents

Description

Venting circuit and method for reducing power consumption of electromagnetic interference filter

The present invention relates to an Electro-Magnetic Interference (EMI) filter, and more particularly to a bleeder circuit and method for reducing the power consumption of an EMI filter.

In recent years, due to the energy crisis and the concept of environmental protection, the EU, North America and Japan have set relevant green environmental regulations for electronic equipment. In addition to the conversion efficiency of electronic equipment, they also impose strict requirements on no-load standby energy consumption. As shown in Fig. 1, the electromagnetic interference filter 12 applied to the power supply device uses a bleeding resistor R1 shunt capacitor Cx in order to prevent the plug from being charged for a long time due to the charge stored in the capacitor Cx after the power plug is removed. To discharge its charge, the EMI filter 12 is in compliance with safety regulations. For example, CEI/IEC 60950-1 clause 2.1.1.7 specifies that the discharge time constant of capacitor Cx and bleeder resistor R1 needs to be less than 1 second. Usually, the bleeder resistor R1 is 2MΩ, and its power consumption is 4~35mW. As long as the AC power supply AC is supplied, the bleeder resistor R1 must always consume energy. When the system is in standby, the power consumption of the bleeder resistor R1 accounts for a considerable proportion of the no-load standby energy consumption.

It is an object of the present invention to provide a bleeder circuit and method for reducing the power consumption of an electromagnetic interference filter.

According to the present invention, a bleeder circuit for reducing power consumption of an electromagnetic interference filter includes a rectifying circuit connected to an ac power supply connected to the EMI filter, and a bleeder resistor and a bleeder switch are connected in series between the rectifying circuit and the ground terminal. To establish or cut off the bleed path, and the detecting circuit controls the bleed switch according to the full wave signal generated by the rectifier circuit.

According to the present invention, a bleeder method for reducing power consumption of an electromagnetic interference filter includes rectifying an alternating current power source connected to the electromagnetic interference filter to generate a full wave signal, and controlling the bleeder switch to establish or cut according to the full wave signal The bleed path.

2 is a bleeder circuit 14 in place of the bleeder resistor R1 of FIG. 1 in accordance with an embodiment of the present invention, which includes a bleeder resistor R2 and a bleeder switch SW connected in series between the rectifier circuit 16 and the ground terminal for venting When the switch SW is closed, a bleed path is established, and when the bleed switch SW is open, the bleed path is cut off. When the AC power supply AC is powered, the voltage across the voltage Vx of the capacitor Cx is rectified into a full-wave signal by the two diodes D1 and D2 in the rectifier circuit 16, and the detection circuit 18 divides the full-wave signal by the voltage divider 20. The full wave signal Vd and the reference voltage Vref are compared with the comparator 22 to produce a comparison signal S1. If the full-wave signal Vd is higher than the reference voltage Vref, the comparison signal S1 is at a high level, and vice versa, at a low level. The detection controller 24 controls the bleeder switch SW according to the comparison signal S1 to control when the bleeder resistor R2 bleeds the charge of the capacitor Cx, thereby reducing the loss caused by the bleeder resistor R2, thereby reducing the no-load standby power consumption.

Figure 3 is a waveform diagram of the circuit of Figure 2. When the AC power supply AC is powered, the comparison signal S1 obtained by comparing the full-wave signal Vd with the reference voltage Vref will continue to switch between the high and low levels, and the time at the high level is T1, during which the bleeder switch SW is open. Therefore, the bleeder resistor R2 is equivalently absent. After the AC power source AC is removed, if the full-wave signal Vd is higher than the reference voltage Vref, the detection controller 24 turns on the bleeder switch SW to discharge the bleeder resistor when the comparison signal S1 is at the high level for more than the delay time T2. R2 bleeds the charge of capacitor Cx, thus causing the discharge time constant of capacitor Cx and bleeder resistor R2 to be less than one second. The delay time T2 can be set according to safety regulations to determine the bleed time. The detection controller 24 to achieve the above functions has a very simple circuit and requires only a countdown or countdown timer, which is well known to those skilled in the art. Preferably, the timer is programmable.

The above description of the preferred embodiments of the present invention is intended to be illustrative, and is not intended to limit the scope of the invention to the disclosed embodiments. It is possible to make modifications or variations based on the above teachings or learning from the embodiments of the present invention. The embodiments are described and illustrated in the practical application of the present invention in various embodiments, and the technical idea of the present invention is determined by the following claims and their equals. .

12. . . Electromagnetic interference filter

14. . . Bleed circuit

16. . . Rectifier circuit

18. . . Detection circuit

20. . . Voltage divider

twenty two. . . Comparators

twenty four. . . Detection controller

Figure 1 is a conventional electromagnetic interference filter;

Figure 2 is an embodiment in accordance with the present invention;

Figure 3 is a waveform diagram of the circuit of Figure 2.

14. . . Bleed circuit

16. . . Rectifier circuit

18. . . Detection circuit

20. . . Voltage divider

twenty two. . . Comparators

twenty four. . . Detection controller

Claims (6)

A bleeder circuit for reducing power consumption of an electromagnetic interference filter, the EMI filter having a capacitor connected between two ends of the AC power source, the bleeder circuit comprising: a rectifier circuit connected between the two ends of the AC power source, To generate a full-wave signal; a bleeder resistor and a bleed switch are connected in series between the rectifier circuit and the ground; and a detection circuit is connected to the rectifier circuit and the bleed switch, and the bleed switch is controlled according to the full-wave signal, the Detector The measuring circuit comprises: a voltage divider connected to the rectifier circuit to divide the full-wave signal; a comparator connected to the voltage divider, comparing the divided full-wave signal and the reference voltage to generate a comparison signal; and detecting The controller is connected to the comparator, and generates a control signal according to the comparison signal to switch the bleed switch. The bleeder circuit of claim 1, wherein the rectifier circuit comprises two diodes. The bleeder circuit of claim 1, wherein the detection controller calculates a time at which the comparison signal maintains a high level, thereby determining the control signal. The bleeder circuit of claim 3, wherein the detection controller includes a timer to determine the control signal. A bleeder method for reducing power consumption of an electromagnetic interference filter, the EMI filter having a capacitor connected between two ends of an AC power source, the bleed method comprising: (A) rectifying the AC power source to generate a full-wave signal And (B) controlling the bleeder switch to establish or cut a bleed path based on the full wave signal; wherein step B includes: The full-wave signal is divided; the divided full-wave signal and the reference voltage are compared to generate a comparison signal; and a control signal is generated according to the comparison signal, and the bleeder resistor is grounded to establish the bleed path. The bleed method of claim 5 further includes calculating a time at which the comparison signal maintains a high level to determine the control signal.