Power converter

• US 7,782,002 B2
• Filed: 09/08/2005
• Issued: 08/24/2010
• Est. Priority Date: 09/08/2004
• Status: Active Grant

• Current Assignee: Progressive Dynamics, Inc.
• Original Assignee: Progressive Dynamics, Inc.
• Inventors: Cook, James C. II
• Primary Examiner(s): Vu; Bao Q
• Application Number:
  US11/221,962
• Publication Number:
  US 20060083031A1
• Time in Patent Office: 1,811 Days
• Field of Search: 318/471, 318/461, 388/800, 388/934
• US Class Current: 318/471
• CPC Class Codes: H02M 1/32 Means for protecting converters other than automatic disconnection
• CPC Class Codes: H02M 3/28 using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
• CPC Class Codes: Y10S 388/934 Thermal condition

Abstract

A switch-type power converter comprising an PET 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. A single thermistor sensor provides inputs to both the fan speed control and a thermal shutdown circuit connected to shut down the gate drives to the FET switch in the event of a high temperature condition. Another shutdown function is provided in response to an input overvoltage condition by way of an operational amplifier. The converter uses foldback for short circuit protection and is compatible with microprocessor units to selectively provide multiple output voltage levels.

Claims

1. A power converter comprising:

an input;

a switch circuit including at least one power transistor;

a controller circuit for cycling the switch circuit in a variable duty cycle mode;

and a step-down transformer having a high voltage primary side connected to the switch circuit and a low voltage secondary side connected to a converter output;

a fan having an electric motor;

a supply circuit connected between the primary side of the transformer and the fan motor; and

a control circuit for operating the fan in a variable speed mode;

wherein the control circuit comprises a comparator having two inputs and an output;

a grounded thermistor connected to one input;

a switch connected in series with the fan motor and the supply circuit; and

the output of the comparator being connected to control the state of the switch to make and break current flow from the supply circuit to the fan motor.

2. A power converter as defined in claim 1 wherein the controller further comprises a heat sink, the thermistor and the at least one power transistor being mounted on the heat sink.

3. A power converter as defined in claim 1 further comprising a shut down circuit including a second set point amplifier connected to receive an input from said thermistor and having an output connected to said controller to stop cycling the switch when the second set point is reached.

14. A power converter as defined in claim 1 wherein the comparator operates in a linear mode over at least part of the fan speed range.

15. A power converter as defined in claim 1 wherein the comparator includes a feedback circuit for operating the fan in a variable duty cycle mode over at least part of the fan speed range.

4. A power converter having an input, an output, a switch including a power transistor, and a controller for operating the switch in a variable duty cycle mode, a temperature sensor and a fan, the power convertor further comprising a step-down transformer having a high voltage primary side connected to the switch and a low voltage secondary side connected to a convertor output;

a supply circuit connected between the primary side of the transformer and the fan,

a first set point device having an input connected to said sensor and an output connected to said fan for changing fan speed; and

a second set point device having an input connected to said sensor, and an output connected to said controller to disable the switch.

5. The converter of claim 4 wherein the first and second set point devices are op-amps.

6. The converter of claim 4 wherein the sensor is a grounded thermistor.

7. The converter of claim 4 further including a housing and a heat sink attached to the housing;

the sensor and the power transistor being mounted in direct thermal exchange with the heat sink.

8. A power converter of claim 7 wherein the ran is mounted to the heat sink.

9. A power converter as defined in claim 8 wherein the heat sink is a finned metal body with a mounting end, the surface of said end being relieved to form an air gap between the fan and the heat sink.

10. A power converter including a power switch, a controller for varying the duty cycle of the switch, a heat sink for the switch and a fan and fan supply voltage source for causing the fan to cause air to flow over the heat sink, the converter further comprising:

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;

wherein the control circuit includes an op-amp, the sensor being grounded and connected to provide an input to the op amp and the op amp being connected to regulate the fan supply voltage wherein the op an includes a feedback circuit which produces an oscillatory output from the op amp.

11. A power converter as defined in claim 10 further including a second op-amp having an input connected to the sensor, said second op-amp being connected to a shut down pin in said controller.

12. A converter as defined in claim 11 wherein the heat sink is a finned metal body;

said switch having at least one current-carrying component attached to the heat sink.

13. A converter as defined in claim 12 further including a spring clip attaching said one component to the heat sink.

16. A power converter comprising an input;

a switching circuit including two power transistors;

a controller circuit for cycling the switching circuit in a variable duty cycle mode;

a step-down transformer having a high voltage primary side connected to receive current pulses from the switching circuit amid a low voltage secondary side connected to a convertor output;

a fan having an electric motor;

a supply circuit connected between the primary side of the transformer and the fan motor;

a first control circuit for operating the fan in a variable speed mode and including a grounded thermistor connected to one input of the control circuit; and

a second control circuit;

the thermistor being connected to an input of the second control circuit and wherein the output of the second control circuit is connected to the controller to stop cycling the switching circuit in response to an excessive temperature condition.