GB2579931A

GB2579931A - A threshold detector circuit for lossless switching

Info

Publication number: GB2579931A
Application number: GB2002624.1A
Authority: GB
Inventors: John Peto Raymond
Original assignee: Quepal Ltd
Current assignee: Quepal Ltd
Priority date: 2017-07-25
Filing date: 2018-07-20
Publication date: 2020-07-08
Also published as: GB2565760A; WO2019021138A3; GB201711925D0; GB202002624D0; WO2019021138A2

Abstract

A threshold detector circuit is described which is suitable for lossless switching of a transistor. The circuit senses a voltage across the transistor and is operative such that when the voltage across the transistor exceeds a user defined HIGH threshold, the threshold detector circuit remains in a quiescent state with a low input impedance to a signal to the detector circuit. When the voltage across the transistor (collector-emitter or drain-source) is less than a user defined LOW threshold, the threshold detector circuit switches to an active state, so that the transistor is switched on thereby creating a low input impedance to a signal to the detector circuit. The continual isolation of the detector circuit from the transistor ensures that there is minimal noise passing to/from the transistor.

Claims

Claims

1 . A threshold detector circuit (Fig 9) for lossless switching of a transistor (Qx) senses a voltage across the transistor (collector-emitter or drain-source) and is operative such that when the voltage across the transistor exceeds a user defined HIGH threshold, the threshold detector circuit remains in a quiescent state with a low input impedance to a signal to the detector circuit; and when the voltage across the transistor (collector-emitter or drain-source) is less than a user defined LOW threshold, the threshold detector circuit (Fig 9) switches to an active state, so that the transistor (QX) is switched on thereby creating a low input impedance to a signal to the detector circuit, thereby continually isolating the detector circuit from noise from its connection to the transistor (QX).
2. A threshold detector circuit according to claim 1 wherein the transistor (Qx) remains switched on until it receives a reset command from a controller (Figs 14A to 14H).
3. A threshold detector circuit according to any preceding claim wherein during the quiescent state, the low input impedance to the signal to the detector circuit from the transistor, is provided by a switchable low impedance circuit (ZD1 , D5, R9 and Q2); and in the active state, the low input impedance to a signal to the detector circuit from the transistor, is provided by the switch (Qx) when the switchable low impedance circuit (ZD1 , D5, R9 and Q2) is disabled.
4. A threshold detector circuit according to any preceding claim includes a soft start circuit.
5. A threshold detector circuit according to any preceding claim wherein a decision to apply a quasi-sine input drive signal or a pure sine input drive signal is determined in accordance with a self-adjusting detection circuit.
6. A threshold detector circuit according to any preceding claim wherein an over-ride switch is configured to switch on/off when a negative drive current is sensed.
7. A threshold detector circuit according to any preceding claim includes a means for over current detection.
8. A threshold detector circuit according to any preceding claim includes a driver module for a resonant power supply.
9. A threshold detector circuit according to claim 8 includes a driver chip for the resonant power supply.
10. A threshold detector circuit according to any preceding claim wherein a feed-forward input drive signal is generated using a signal derived from an input current signal.
1 1 . A threshold detector circuit according to any preceding claim includes a switch control circuit connected across input terminals of a motor.
12. A threshold detector circuit according to claim 1 1 wherein the feed-forward input drive signal is used to control a means for adjusting a supply voltage in order to vary motor torque at low frequencies.
13. A threshold detector circuit according to either claim 1 1 or 12 wherein a microprocessor generates the feed-forward signal.
14. A threshold detector circuit according to any preceding claim includes at least one shunt capacitor operable to modify the drive voltage from a quasi-sine to approximate to a sine wave.
15. A threshold detector circuit according to any of claims 1 1 to 14 includes a resonant half bridge circuit for converting an applied input voltage and/or an applied input current to the motor in order to supply a turn on current for the motor, at a selected instant, independent of the supply voltage and/or the supply current and/or load of the motor.
16. A threshold detector circuit according to any of claims 1 1 to 15 includes a feedback circuit with a resonant half bridge operable to switch on independently of at least one of the following: motor input voltage, motor load, load current, shunt capacitance, inductance and resistance of the motor.
17. An electrical appliance, such as a pump, tool, drive system or machine, including the threshold detector circuit according to any of claims 1 to 16.
18. A vehicle including the threshold detector circuit and motor of any of claims 1 1 to 16.