DC fan speed control
AssigneeZenith Electronics Corporation
InventorJohn G. Konopka
Life of this patent
Estimating the term…
Abstract
A simple pulse width modulator speed control for a brushless DC "pancake" type fan motor utilizes a type 555 timer for driving a transistor switch, connected in series between the DC voltage supply and the fan motor, at about a 10 Hz rate. The duty cycle of the pulsed output of the timer is controllable by a variable resistor, which in the preferred embodiment comprises a thermistor for controlling the fan speed as a function of temperature. The fan motor is restarted on each cycle of full voltage amplitude pulses and consequently will start under all operating conditions.
Claims3
A speed control for a DC fan motor comprising:
- a source of DC voltage;
- a switch transistor connected in series with said motor and said voltage source;
- a type 555 timer including an RC circuit coupled to said voltage source for developing a constant amplitude pulsed voltage output;
- means for operating said switch transistor which said pulsed voltage output;
- and
- means for varying the on/off cycle of said timer, said RC circuit including a thermistor for changing the speed of said motor as a function of temperature, said speed control consisting of two capacitors and two resistors in addition to said switch transistor said 555 timer, and said thermistor.
A speed control for a brushless DC fan motor comprising:
- a source of DC voltage;
- a switch transistor having a base and an emitter-collector path connected in series with said voltage source and said motor;
- a type 555 timer coupled to said DC voltage source and to said base of said switch transistor, said timer supplying constant amplitude voltage pulses to said transistor at approximately a 10 Hz rate;
- an RC circuit coupled to said timer for varying the duty cycle thereof;
- and
- a thermistor in said RC circuit for controlling the speed of said motor as a function of temperature.
Dependencies are inferred from the claim text.