On high-frequency switching power supplies, the input voltage’s frequency is increased before going into the transformer, allowing the transformer and the electrolytic capacitor to be very small. This means a SMPS uses less copper, and it costs less to ship them to us from China.
Here is how simple switching mode power supply works.
1. The AC power-line voltage enters the power supply, and is rectified and filtered to DC.
2. The DC is “chopped” into pulses (converted to high-frequency AC) by transistor switches.
3. The ultrasonic AC goes through a lightweight isolation transformer.
4. The transformer output is rectified and filtered to the correct DC voltage for the amplifier.
5. The output voltage is then fed to the power-amp circuits. The switches dissipate very little power when they are on or off, which results in high efficiency, eg smaller size and less heat.
Switching power supplies typically have higher voltages present, typically half of the line voltage being supplied. This means a more dangerous environment inside the power supply enclosure.
Another issue is the high frequencies associated with SMPS. Some security electronics are sensitive to these high frequencies.
Finally, switching mode power supplies have a reputation for producing huge transient spikes on their outputs in the course of failing in service. This results in damage to other hardware in addition to the interruption of operation of the system to which it is connected. Linear power supplies fail too, only they do not usually shoot surges out into other gear.
Which power supply design is best? There is a time and place for both types.
The new Honeywell Power Products HPFF8 (FireForce 8) power supply is designed to provide installers substantial time-saving benefits when expanding fire alarm NACs (notification appliance circuits) and provide auxiliary power to 24-volt system accessories. HPFF8 supplies can be activated by any 12- or 24-Volt fire alarm control panel or operate alone. The HPFF8 also offers an exclusive EOL (end-of-line) resistor replacement and NAC trouble memory features.
One of the most challenging aspects of a retrofit application is locating the existing EOL resistor.
The HPFF8’s EOL resistor replacement feature is designed to save security technicians hours of searching for the pre-existing EOL resistor. In retrofit applications, a single resistor matching the existing EOL can be used as a reference EOL for all outputs. This feature speeds installation and system checkout.
Frequently, NAC trouble alarms clear themselves prior to a maintenance call. Feedback collected through Honeywell Power Products’ Voice of the Customer process indicated a need for fire alarm technicians to identify the source of NAC troubles on-site. The HPFF8 includes a trouble memory feature that displays past troubles (by NAC) for rapid installer diagnostics. This feature allows technicians to investigate the source of recurring troubles and prevent future false alarms.
Available in 8-amp, it provides regulated and filtered 24 VDC power, each of 4 NAC’s are rated at 3.0 Amp with aux power rated 1.5 Amp.
The outputs may be configured as: four Class B (Style W, X, Y); or two Class A (Style Z); or two Class B and one Class A; or four Class A (Style Z) with the optional Class A adaptor installed.
They also contain a battery charger capable of charging up to 26 Amp Hour batteries.
These supplies are commonly used for NAC device synchronization to meet ADA (Americans with Disabilities Act) requirements.
The HPFF8 features field-selectable, built-in strobe and horn synchronization protocols, and a pass-through feature that allows a pre-generated sync protocol to pass from another synchronization source.
The independent horn silencing feature allows synchronized horns and strobes that operate on a single circuit to have the horns silenced via sync protocol.
For enhanced notification appliance circuit survivability, dual-activation inputs can be utilized for redundant trip operation.
Information: www.honeywellpower.com. or phone 877-477-7697.
Power supplies come in two basic designs – linear and switching – both with advantages and disadvantages. Which power supply design is best? There is a time and place for both types.