Power converter

Abstract

A switch-type power converter includes a double FET switch operating in a variable duty cycle mode under the control of a Unitrode 3846 integrated circuit controller. Indications of excess input voltage and reverse battery connections are provided by circuits including an element which permanently changes state. A cooling fan mounted on a finned heat sink is operated in a variable speed mode.

1 . A power converter having an input for receiving a supply voltage, a switch, and a duty cycle controller connected to control the switch to regulate an output voltage produced by the converter wherein the improvement comprises:
 a first circuit connected to said input and responsive to a first level over-voltage condition at said input for altering operation of duty cycle controller; and   a second circuit connected to said input and responsive to a second level over-voltage condition at said input to irreversibly change state without altering operation of the duty cycle controller.   
   
   
       2 . A converter as described in  claim 1  wherein the second level is higher than the first level. 
   
   
       3 . A power converter as described in  claim 1  wherein the first circuit comprises an amplifier, circuit connected to said input and to a reference voltage, said amplifier circuit having an output connected to said controller to shut, said controller down in response to the first level over-voltage condition. 
   
   
       4 . A power converter as described in  claim 1  wherein the second circuit comprises the series combination of a non-resettable fuse and a Zener diode connected between said input and ground. 
   
   
       5 . A power converter having an input connectible to an AC line voltage source, a rectifier for converting an AC line voltage to DC, a switching circuit comprising at least one power transistor, a transformer having a primary side connected to said rectifier and to said switch circuit and a secondary side connected to a converter output, a controller circuit for operating said switch circuit in a variable duty cycle mode wherein the improvement comprises:
 a permanent over-voltage indicator circuit connected between said rectifier and ground and including the series combination of a voltage responsive semi-conductor device and an element which irreversibly changes state in response to the presence of an over-voltage condition at said rectifier output.   
   
   
       6 . The power converter described in  claim 5  wherein said element is a fuse. 
   
   
       7 . The power converter described in  claim 5  wherein said semi-conductor device is a Zener diode. 
   
   
       8 . The power converter of  claim 5  further comprising an over-voltage shut-down circuit connected between said rectifier output and said controller for shutting the controller down under over-voltage conditions. 
   
   
       9 . The power converter of  claim 8  wherein said over-voltage shut-down circuit further includes an operational amplifier. 
   
   
       10 . A power converter comprising an input for receiving a supply voltage, a switch including at least one power transistor, and a duty cycle controller connected to cycle the switch on and off; an over-voltage shut-down circuit connected between said input and said controller and comprising an operational amplifier; said operational amplifier having an output, connected to a shut down pin of said controller to terminate cycling of the switch. 
   
   
       11 . A power converter for charging a battery and having a switch, a duty cycle controller connected to the switch, a transformer having a primary side and a secondary side, an output inductor, the primary side being connected to the switch and the secondary side being connected to the output inductor, a circuit for indicating a reverse battery connection and comprising a device connected between the output inductor and ground and effective to irreversibly change state when a reverse battery connection is made. 
   
   
       12 . A power converter as defined in  claim 11  further including a capacitor connected in parallel with said device. 
   
   
       13 . A power converter as defined in  claim 12  wherein the device is a Schottky diode. 
   
   
       14 . A power converter comprising a switch, a controller for controlling the duty cycle of the switch, a transformer, an output inductor and a converter output terminal;
 a circuit board having conductive traces formed thereon, the inductor being mounted on the current board such that at least one conductive trace runs from the inductor to the output terminal; and   a heavy gauge wire conductively bonded to and along said one conductive trace.   
   
   
       15 . A power converter comprising a switch, a controller for controlling the duty cycle of the switch, a transformer, an output inductor and a converter output terminal;
 a circuit board having conductive traces formed thereon, at least one trace running from the transformer to the output terminal; and   a heavy gauge wire conductively bonded to and along said one conductive trace.   
   
   
       16 . A power converter including a switch, a controller for varying the duty cycle of the switch, a heat sink for the switch, a fan for causing the fan to cause air to flow over the heat sink;
 a heat sensor; and   a fan control circuit, the fan control circuit being operative to control the supply voltage source to vary the speed of the fan in response to increasing temperature of said sensor.   
   
   
       17 . The power converter defined in  claim 16  wherein the fan comprises a motor mounted proximate the heat sink, the heat sink comprises a metal extrusion having a recess machined into an end thereof to provide an air gap between the heat sink and the fan motor.