Browse Prior Art Database

Power Supply for In-Line Two-Wire Switch

IP.com Disclosure Number: IPCOM000116561D
Original Publication Date: 1995-Oct-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 88K

Publishing Venue

IBM

Related People

Beavillier, L: AUTHOR [+3]

Abstract

In an application where power to electrical baseboard heater is controlled by an in-line electronic thermostat, there is a need to provide a low-voltage supply for the electronic circuitry of the thermostat without having an external source, such as a battery.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Power Supply for In-Line Two-Wire Switch

      In an application where power to electrical baseboard heater is
controlled by an in-line electronic thermostat, there is a need to
provide a low-voltage supply for the electronic circuitry of the
thermostat without having an external source, such as a battery.

      Such a supply can be provided by using a small portion of the
energy of each cycle of the main power supplied to the heater without
disrupting the normal operation of the heater, without unbalancing
the supply to the heater and without introducing or creating adverse
effects on the power mains such as by the introduction of unwanted
harmonics.

This power supply meets the following standards:
  o  High-frequency emission: CSA C108.8-M1983 class B; FCC part 15
      class B
  o  Voltage/current harmonics requirements:  CEI 555-2
  o  Lightning surge immunity: IEEE 62.41 class B3
  o  Electrical fast transient / Burst requirement: CEI 801-4 1988
      class 3
  o  High frequency noise on network: TAD-84-65
  o  Power line disturbance: IBM PLD
  o  Radiated susceptibility: CEI 801-3 class 2 and class 3

The power supply can operate from 24 to 300 VAC with the existing
components.

      The AC/DC converter U2 is used in a conventional way when the
TRIAC is OFF.  At zero crossing, the C1 capacitor is charged through
U2 and R3, up to approximately 13 volts.  The C1 voltage is then
regulated by U2 at 5 volts  10mv.  The charging current is limited
by R3.

      When the TRIAC is ON, the required voltage to charge C1 through
R3 and U2 is no longer present.  Consequently, the AC/DC converter
cannot be used in a conventional manner, thus phase monitoring is
used to recharge C1.

      To reduce the TRIAC closing voltage, capacitor C1 is quickly
charged.  For this step, C1 is connected directly to the line voltage
through D5 and SCR U6.  C1 is charged only at the zero crossing of
the power supply.

      Capacitor C1 is charged to a voltage of approximately 7 volts.
Current passes through U6 and D5 when a sign...