HV9901DB1
Universal Relay Driver
Introduction
The HV9901 is a universal relay driver employing PWM
switching techniques utilizing the relay coil聮s inductance to
provide efficient operation over a wide supply voltage range.
Relay drive is constant-current. Pull-in current, pull-in time,
and hold current are all programmable via 2 resistors and a
capacitor. An adjustable regulator provides 1mA for external
circuitry.
The HV9901DB1 demo board contains all the circuitry
necessary to demonstrate the operation of the HV9901.
Included on-board are a full-wave input rectifier, fuse, the
HV9901, and a 10A relay. Provisions for connecting an
external relay are available. The circuit may be modified to
accomodate the drive requirements of other relays.
WARNING!!!
Do not connect earth-grounded
instruments when connected to the
AC line. Doing so will short the AC
line, resulting in damage to the demo
board and/or the instrument. Use an
isolation transformer on the AC line,
use high voltage differential probes,
or use a floating instrument to make
measurements when connected to
the AC line.
Specifications
Relay Drive Current
Pull-in Time
Contact Form
Input Voltage
10聳400VDC, 24聳277VAC
72mA pull-in, 24mA hold
20ms
Contact Rating
Enable
Auxillary Regulator (V
CC
)
10A@125VAC, 6A@277VAC
<1.5V off, >3.5V on
5.0V@1mA
SPDT (1FormC)
Switching Frequency
21kHz
Board Layout and Connections
Input
Voltage
Common
D2
F1
~
~
D1
+
聳
Enable Polarity
Selector
IC1
R3 R1
C4
R7
C5
C2
R2
R4
C3
Relay
Contacts
Normally Closed
C1
K1
D3
Q1
R5
Normally Open
Relay
Selector
R6
WARNING!!!
No galvanic isolation. Dangerous voltages
are present when connected to the AC line.
Input Voltage
External
Relay
Sync
Enable
V
CC
Ground
Supply voltage. May be a DC source in the range of
10聳400VDC, or an AC source in the range of 24聳277VACrms.
A full-wave bridge rectifier on board rectifies the AC. Also
included is a 250mA 2AG fuse.
Relay Contacts
For connecting an external load. The PCB traces are rated at
10A for a 20擄C rise.
Relay Selector
In the
Int
position, the on-board relay is operated. In the
Ext
position, a relay connected to the External Relay terminals is
operated.
External Relay
For connection of an off-board relay.
Sync
Synchronizes multiple HV9901s to the same frequency or to a
master clock. Frequency will be the highest independent
frequency. Connect to the Sync pins of other HV9901s or to a
master clock.
Enable
Logic-level enable for relay operation. See
Enable Polarity
Selector
for polarity.
V
CC
Supplies 5V at 1mA for external circuitry.
Ground
Circuit common.
Since galvanic isolation is not provided,
ground will be at the AC line potential!
Enable Polarity Selector
Sets Enable polarity. In the
0
position, Enable is active low. In
the
1
position, Enable is active high.
1
2
