Switching Power Supply With Overvoltage Protection And Overvoltage Protection Method Thereof

• US 20090152950A1
• Filed: 01/06/2006
• Published: 06/18/2009
• Est. Priority Date: 01/08/2005
• Status: Active Grant

• Current Assignee: Vertiv Corporation (Vertiv Holdings Co.)
• Original Assignee: Emerson Network Power Energy Systems AB (Vertiv Holdings Co.)
• Inventors: Ru, Yonggang, Zhang, Huajian, Chen, Baoguo, Yu, Shiqiang
• Granted Patent: US 7,932,632 B2
• Time in Patent Office: Days
• US Class Current: 307/43
• CPC Class Codes: H02H 7/1213 for DC-DC converters
• CPC Class Codes: H02H 9/001 limiting speed of change of electric quantities, e.g. soft switching on or off progressive control of electronic switches for eliminating interferences H03K17/16
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 1/36 Means for starting or stopping converters

Abstract

A switching power supply with overvoltage protection includes a soft start circuit, a rectifying circuit, a filter capacitor, a main supply, an auxiliary supply and a monitoring circuit. When the input voltage is higher than the predetermined protection voltage, a first electric control switch is turned off, and the main power circuit of the switching power supply is shut off. At the moment, the actuation and release of the second electric control switch is controlled so as to control the input power supply to intermittently charge the power supply module such that the output voltage downstream of the rectifying circuit inside the power supply is controlled in a safe range. For instance, the second electric control is turned on when the output voltage is lower than a certain value, and is turned off when the output voltage is higher than a certain value. Thus, it is ensured that the bus line voltage inside the power supply is controlled within a safe range, to ensure the safety of the devices inside the power supply; and at the same time to ensure the safety of the inner devices of the switching power supply, such that the auxiliary power supply and the control circuit can work normally.

Claims

1. A switching power supply with overvoltage protection, comprising a soft start circuit (1), a rectifying circuit (2), a filter capacitor (C1), a main power supply (3), an auxiliary power supply (4) and a monitoring circuit (10);

the soft start circuit (1) comprising a soft start resistor (Z1) and a first electric control switch (K1) positioned in a branch in parallel with the soft start resistor (Z1);

wherein after an AC current is input into the rectifying circuit (2) for rectification and into the filter capacitor (C1) for filtering via the soft start circuit (1), a resulted DC current is output to the main power supply (3) and the auxiliary power supply (4) respectively;

the auxiliary power supply (4) supplying DC voltage to the monitoring circuit (10), while the monitoring circuit (10) monitoring an input or/and output voltage of the switching power supply, and controlling the first electric control switch (K1) in the soft start circuit (1);

characterized in that a second electric control switch (K2) is provided, wherein the second electric control switch (K2) is connected in series on a phase line on which the soft start resistor (Z1) is provided, the control end of the second electric control switch (K2) is connected with the monitoring circuit (10), the monitoring circuit (10) controlling an ON or OFF state of the second electric control switch (K2).

2. The switching power supply with overvoltage protection according to claim 1, characterized in that the second electric control switch (K2) and the soft start resistor (Z1) are connected in series, and the serial branch is connected with the first electric control switch (K1) in parallel.

3. The switching power supply with overvoltage protection according to claim 1, further comprising a second impedance (Z2) connected in parallel with the second electric switch (K2).

4. The switching power supply with overvoltage protection according to claim 1, further comprising a second impedance (Z2) and a third impedance (Z3), the third impedance (Z3) and the second electric control switch (K2) being connected in series, and then being connected with the second impedance (Z2) in parallel.

5. The switching power supply with overvoltage protection according to claim 1, further comprising a second auxiliary power supply (6), an input end of which is connected with a battery, while an output end of which is connected with the monitoring circuit (10).

6. The switching power supply with overvoltage protection according to claim 1, characterized in that the first and second electric control switches (K1, K2) are relays.

7. An overvoltage protection method for a switching power supply, comprising the following steps:

S1;

a monitoring circuit (10) monitors an input voltage or/and output voltage of a switching power supply;

S2;

if AC input is in an allowable range, then ON and OFF states of a first electric control switch (K1) of normal open type and a second electric control switch (K2) of normal close type is controlled such that AC charges a filter capacitor (C1) through a soft start resistor (Z1) and the second electric control switch (K2), after completion of a soft start, the first electric control switch (K1) is controlled to be turned on and a module enters a normal operating state;

S3;

when the AC input is in the situation of overvoltage, voltage of the filter capacitor (C1) rises, if the monitoring circuit (10) detects that the voltage of the filtering capacitor (C1) is higher than a predetermined voltage threshold, the control circuit (10) cuts off the first and second electric control switches K1 and K2, and the energy stored in the filter capacitor (C1) maintains the OFF state of the second electric control switch (K2);

S4;

when the energy stored in the filter capacitor (C1) is consumed and the voltage thereof is lowered to a certain threshold, the second electric control switch (K2) returns to the ON state such that AC charges the filter capacitor (C1) through the soft start resistor (Z1) and the second electric control switch (K2), and thereby the voltage of the filtering capacitor (C1) rises gradually;

S5;

if the voltage of the filter capacitor (C1) exceeds the allowable value again, the second electric control switch (K2) will be cut off again and the aforesaid steps S3 and S4 repeat;

S6;

until the voltage of AC input decreases to be in a normal range, the states of the first and second electric control switches K1 and K2 are controlled such that the module enters a normal operating state.

8. The overvoltage protection method for a switching power supply according to claim 7, characterized in that a second voltage threshold is set in the monitoring device (10) in advance, such that in step S4, the second electric control switch (K2) is controlled by the monitoring circuit (10) to return to the ON state when it is detected that the voltage is lower than the threshold.

9. The overvoltage protection method for a switching power supply according to claim 7, characterized in that a time of turning on or cutting off of the first and second electric control switches (K1, K2) is set such that the input voltage at the time is lower than a bus line voltage, and thus the current is zero when a relay is actuated or released.