Switching regulator with base charge removal circuit
First Claim
1. In a switching regulator wherein the on-off operation of a first switching transistor is controlled in response to an error signal detected in DC load voltage to regulate the load voltage at a constant level, the improvement comprising a circuit for controlling said first switching transistor, which comprises:
- square-wave pulse generating means for generating AC square-wave pulses at a constant repetition frequency;
triangular-wave forming means for forming triangular-wave pulses from said square-wave pulses;
means including diode means and capacitance means connected in series with one another between output terminals of said square-wave pulse generating means, for providing a voltage potential at a common connection point between said diode means and said capacitance means, said voltage potential being negative in relation to the output voltage of said triangular-wave forming means; and
variable impedance means connected between the output of said triangular-wave forming means and said common connection point at the negative voltage potential so that the triangular-wave pulses are biased to be negative in voltage potential at each valley of the triangular-wave pulses, said variable impedance means being operative to vary its impedance in response to the error signal, the biased triangular-wave pulses produced by said variable impedance means providing a control signal coupled to said first switching transistor for controlling turn-on and off operation of said first switching transistor.
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Accused Products
Abstract
A control circuit for a main switching transistor in a switching regulator, wherein PWM pulses are produced by varying a DC bias of triangular-wave pulses in response to a detected error signal, and which pulses are provided as a control signal for switching on and off the main switching transistor. In order to reduce power dissipation due to carrier storage at each turn-off operation of the switching transistor, a negative voltage potential is produced by a diode and a capacitor from square-wave pulses of a constant repetition frequency from which pulses the triangular-wave pulses are formed, and is applied to an emitter of an NPN transistor which operates as a variable impedance circuit for varying the DC bias of the triangular-wave pulses in response to the error signal, so that the triangular-wave pulses are biased to a negative voltage potential. Therefore, the base of the switching transistor rapidly drops down to a negative voltage potential at the time of each turn-off operation of the switching transistor, so that the stored carrier is rapidly drawn out of the base of the switching transistor.
22 Citations
10 Claims
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1. In a switching regulator wherein the on-off operation of a first switching transistor is controlled in response to an error signal detected in DC load voltage to regulate the load voltage at a constant level, the improvement comprising a circuit for controlling said first switching transistor, which comprises:
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square-wave pulse generating means for generating AC square-wave pulses at a constant repetition frequency; triangular-wave forming means for forming triangular-wave pulses from said square-wave pulses; means including diode means and capacitance means connected in series with one another between output terminals of said square-wave pulse generating means, for providing a voltage potential at a common connection point between said diode means and said capacitance means, said voltage potential being negative in relation to the output voltage of said triangular-wave forming means; and variable impedance means connected between the output of said triangular-wave forming means and said common connection point at the negative voltage potential so that the triangular-wave pulses are biased to be negative in voltage potential at each valley of the triangular-wave pulses, said variable impedance means being operative to vary its impedance in response to the error signal, the biased triangular-wave pulses produced by said variable impedance means providing a control signal coupled to said first switching transistor for controlling turn-on and off operation of said first switching transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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Specification