# Brown-out circuit

Discussion in 'General Electronics Chat' started by kamalakgkannan, Jul 2, 2005.

1. ### kamalakgkannan Thread Starter New Member

Jul 2, 2005
8
0
Can anyone help me in providing information about different kinds of brownout circuitries used in the electronic modules to shutdown the system in case of lower input voltages

2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
Hi,

It would be helpful to know what you are interested in protecting.

In general, there are methods that just shut things down when the line voltage gets low. A simple drop out relay can do this. At the advanced end are uninterruptable power supplies (UPS) that will supply the proper line voltage to the load even if line power drops completely. These can supply humdreds of watts up to ten of thousands of watts of power.

3. ### kamalakgkannan Thread Starter New Member

Jul 2, 2005
8
0
Hi,

Let me be brief my requirement. For example to say if I am using an electronic controls(Microcontroller based) for a refrigerator, if the input voltage keeps on reducing to a value that the compressor to perform inefficiently. Say the operating voltage range for the refrigerator to be 180Volts to 260Volts, in case if the voltage goes down below 180Volts, I have to shutdown all the loads of the appliance and backup the status of the machine at that instant in the microcontroller memory and the electronic control should get into a standby mode. My question is how to sense(accurately) this high voltage(AC) and feed to the microcontroller(DC Voltage).

4. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
Hi,

You could use a transformer to reduce the AC. Rectify and filter the low-voltage AC into DC. Use part of the DC through a regulator to power a voltage comparator. Run the DC off the filter caps through a resistive divider to some lower value, and monitor it with the comparator. Use the regulated voltage and a trimmer to set the trip point. When the AC voltage goes down to 180, the comparator will change state. Monitor the comparator output with your microprocessor and shut down when the comparator indicates the AC level is low.