An inverter includes first, second, and third dc voltage sources, first and second switching elements which are connected in series to the first dc voltage source, a signal generator section for producing first and second control signals on the basis of the output voltage from the third dc voltage source, first and second signal level converter sections for converting voltage levels of the first and second control signals based on the output voltage from the second dc voltage source and thereby respectively generating first and second output signals, and first and second driver sections responsive to the first and second output signals for supplying the first and second switching element with first and second driving signals on the basis of the output voltage from the second dc voltage source and thereby respectively turning the first and second switching elements on or off. At least either one of the first and second signal level converter sections includes a turn-off section responsive when at least either one of the output voltages respectively from the second and third dc voltage sources is lower than a predetermined voltage level for turning the first or second switching element off irrespective of the first and second control signals.
A power converting apparatus comprises a converter, a control device, and a protection device. The converter has first and second semiconductor devices coupled in series. The control device outputs a plurality of control signals for switching on the first and second semiconductor devices. The protection device detects the control signals and cuts off the control signals for the first and second semiconductor devices when the control signals for the first and second semiconductor devices are detected simultaneously.
A power conversion device of the inverter type for three-phase DC motor includes three parallel pairs of output transistors between a power supply voltage and the ground potential. These pairs provide three upper-stage transistors and three lower-stage transistors with diodes being coupled thereto. Drivers are connected to the transistors respectively. A capacitor for each upper-stage driver has an electrode coupled to the power supply voltage and the other electrode coupled to the ground through a corresponding lower-stage transistor. A controller controls the upper- and lower-stage drivers in response to a pulse width modulation (PWM) signal generated by a PWM generator to represent a desired motor rotation speed. The upper-stage transistors are PWM-driven so that each one turns on and off repeatedly during a 120-degree electrical angle period. While one upper-stage transistor is PWM-driven during a 120-degree period, a corresponding lower-stage transistor turns on in response to a reverse-phased pulse at the beginning of this period, thereby charging the capacitor.
The present invention provides an electric motor movement controlling method, where the electric motor is fed by a total voltage proportional to the network voltage. The method comprises steps of making a first measurement of level of the network voltage at a first moment of measurement and making a second measurement of level of the network voltage; at a second moment of measurement, calculating the value of the derivative of the values of voltage measured in function of the first and second moments of measurement, to obtain a value of a proportional network voltage, and altering the value of the total voltage fed to the motor, proportionally to the value of the proportional network. A system that will implement the steps of the method of the present invention, as well as a compressor comprising the system of the present invention are foreseen.
A controller for controlling a power device in response to an input signal includes a first signal generator for generating a first signal in response to the input signal; a level shifter for changing an output level of the first signal to a value which is a function of a first main power supply potential in order to produce a second signal; and a first control signal generator for generating the control signal for a first semiconductor device in response to the second signal. The level shifter includes at least one level shifting semiconductor element wherein the semiconductor element is controlled by the first signal and the at least one level shifting semiconductor element exhibiting breakdown voltage characteristics whereby a breakdown voltage has a value not less than a voltage in the range between a value of the first and a value of a second main power supply potential.
An inverter apparatus includes a flip-flop circuit and a voltage clamp circuit disposed in the upper arm, and set and reset signal generators each having a series connection of two switching devices. By using an input signal and using an output signal of the flip-flop circuit, the above described two switching devices are activated in a complementary manner. Owing to this configuration, no current flows except a minute time for supplying a trigger signal to the flip-flop circuit, resulting in low current consumption. If the output logic of the flip-flop circuit has been inverted by noise, two switching devices are simultaneously in the on-state and a re-trigger current is let flow to restore the above described output logic to the normal state, resulting in the complementary state again. As a result, signal transmission between the upper and lower arms is performed at higher speed and with a lower loss. In addition, the inverter apparatus is protected from false operation due to noise.
